Bug Eric

Bereavement

2012-01-28T22:31:00.000-08:00

There will be no posts in the immediate future, due to a family emergency. Heidi and I appreciate your prayers for the Geske and Genter families in the meantime. Thank you.

Wasp Wednesday: Diapriids

2012-01-25T06:00:00.000-08:00

Few insects, unfortunately, have common names in the English language. That creates an obstacle for the general public to realize just how diverse and amazing the animal kingdom truly is. Among these overlooked organisms are tiny wasps in the family Diapriidae. I was not even familiar with them myself until I ran across numerous specimens while sorting pitfall and emergence trap samples for the University of Massachusetts back in 2009.

Were I to name them, I would call them “shelf-faced wasps.” Well, it fits! The most prominent feature of these insects is a ledge-like extension of the face just above the clypeus (“upper lip,” if you will), from which the antennae originate. Not all diapriids have this feature, but most of our more than 300 North American species do.

Averaging only 2-4 millimeters in length (they range from one to eight millimeters), it helps to put them under a microscope to see the details of their external anatomy. Besides the face, note that there is minimal wing venation, if any at all. The abdomen is petiolate, and the body is generally smooth and polished.

Little is known about these parasitic wasps in part because they do not impact important agricultural pests. Instead, most known species have a life cycle involving parasitism of the larvae and/or pupae of various flies (order Diptera). Fungus gnats (families Mycetophilidae and Sciaridae) are among common hosts. The larva of the diapriid feeds internally on the maggot. While most are probably solitary parasites, at least a few species are gregarious, several larvae feeding inside one host.

Diapriids are most common in moist woodland habitats where they stalk their hosts around fungi, leaf litter, and damp soil. Some genera in occupy extreme habitats such as intertidal zones. There are at least two records from the Old World tropics suggesting that some specialized genera in the subfamily Diapriinae are parasitic on the larvae of certain ants.

The great majority of diapriid species are awaiting formal description by scientists. Worldwide, there are 2,300 described species in 150 genera. Entomologists estimate there are at least 4,500 species. There are few resources for identifying species outside of Europe.

I urge my fellow naturalists to try various trapping techniques to see what wonders they might find in their own yard, garden, or nearby park. Invest in a good microscope, too. You will be surprised at the animals you will find.

Sources: Goulet, Henri and John T. Huber (eds.). 1993. Hymenoptera of the World: An identification guide to families. Ottawa: Agriculture Canada. 668 pp.
The Diapriidae

Spider Sunday: Giant Crab Spider

2012-01-22T06:00:00.000-08:00

When one thinks of giant spiders in the southwest U.S., tarantulas come immediately to mind. There is one other spider, however, in an unrelated family, that rivals tarantulas in size. Olios giganteus is a member of the family Sparassidae, collectively known as “giant crab spiders,” or “huntsman” spiders. These are tropical and subtropical spiders, but some species occasionally turn up in temperate climates, imported with bananas or other tropical fruits.

Giant crab spiders, like spiders in the families Thomisidae, Philodromidae (see Ebo from last week’s “Spider Sunday”), and Selenopidae, have laterigrade legs. This means the legs are “twisted” at the base such that they are oriented in the horizontal plane, rather than the vertical axis. This allows these flat-bodied spiders to scuttle into very narrow cracks or crevices. Giant crab spiders take full advantage of this to slip underneath loose bark, or into an opening in the siding on your home. Indeed, you are most often apt to encounter these spiders on vertical surfaces.

Paired claws at the tip of each leg, with a tuft of special hairs between them, allow the spider to easily navigate surfaces with the least bit of texture, or scramble effortlessly over slender twigs in pursuit of prey. Hiding by day they emerge at night to hunt. I was surprised to find them on a night hike in Florida Canyon in the Santa Rita Mountains of Arizona, so accustomed had I become to seeing them on the exterior walls of buildings.

They do sometimes stray indoors, and apparently such incidents once inspired newspaper publicity for the “barking spider” in some small towns in west Texas (Gertsch, 1979).

There are five species in the genus Olios found in North America north of Mexico, collectively found from southern California to western Texas. O. giganteus is recorded from California, Nevada, Utah, Arizona, New Mexico, extreme west Texas (Big Bend), and Sonora, Mexico. U.S. specimens formerly classified as O. fasciculatus, an African species, are now known to be O. giganteus.

Olios giganteus is just that: a giant. Mature males measure 11.3-29.4 mm (average 25), but females can be 14.6 to a whopping 48 millimeters (average 31.6) in body length. The eight sprawling legs make these arachnids look larger still. In reality, their legspan is “only” 50-64 millimeters.

Little is known about the life cycle of Olios huntsman spiders. Normally nomadic, females do settle down when it comes time to lay eggs. They weave a large bag-like retreat within which they spin an egg sac. They guard the precious pouch and the spiderlings that eventually emerge, not feeding themselves during the incubation period, about one month in mid-late summer (Jennings, 1981).

Sources: Rheims, Cristina A. 2010. “On the native Nearctic species of the huntsman spider family Sparassidae Bertkau (Araneae),” J. Arachnol. 38: 530-537
Lizotte, Rene. 2000. “Spiders” in Phillips, Steven J. and Patricia Wentworth Comus (eds.). A Natural History of the Sonoran Desert. Tucson: Arizona-Sonora Desert Museum Press. pp. 294-303.
Jennings, Daniel T. 1981. “Observations on Olios fasciculatus, a giant crab spider (Araneae: Sparassidae),” The Southwest Naturalist 26(4): 437-439.
Richman, David B., et al. 2008. The Spiders of the Arid Southwest. New Mexico State University.
Gertsch, Willis J. 1979. American Spiders (2nd ed.). New York: Van Nostrand Reinhold Company, Inc. 274 pp.

Wasp Wednesday: Not Wasp VI

2012-01-18T06:00:00.000-08:00

Many bees are easily mistaken for small wasps, especially the “masked bees” of the genus Hylaeus in the family Colletidae. There are not many characters that can be used to separate these bees from wasps that are easily visible in the field. Mostly it just takes a practiced eye to tell them apart.

Masked bees, also known as yellow-faced bees, are nearly hairless, accentuating their resemblance to wasps. While wasps have hairs, too, those hairs are simple and unbranched. The hairs of bees, in contrast, are plumose and almost feather-like. Unfortunately, this character requires a minimum magnification of sixty power to observe. Live bees and wasps don’t usually cooperate for microscopic examination.

Hylaeus are not parasitic on other bees, so a logical question would be how does a hairless bee transport pollen and nectar back to its nest? The answer is that the female bee ingests mostly nectar, and stores it in a special internal organ called the “crop.” Once the bee arrives back at the nest, she regurgitates her load and stores it in a cell. Several such loads will provide enough nourishment for the single larval offspring in each cell.

Masked bees are solitary, meaning each female makes her own nest. Without strong jaws, or a rake of spines on the front legs, Hylaeus bees are pretty much forced to use pre-existing burrows of other insects in the soil, cavities in the pith of twigs, or in abandoned galls. Indeed, most species of Hylaeus nest in hollow stems or twigs. Individual cells are lined with a natural plastic, a type of polymer secreted by glands in the female’s abdomen.

Male and female masked bees can be distinguished by their facial markings. Females generally have yellow, white, or ivory markings on the inner margin of each eye. Males have the entire face colored yellow or white.

Photo by Tom Murray via Bugguide.net

There are around 900 species of Hylaeus, collectively distributed worldwide, with about fifty in North America. The genus reaches its zenith of diversity in subtropical Australia, and the Hawaiian Islands. There are, or were, sixty species in Hawaii. Several of those are threatened or endangered, in part by invasive ant species that have been introduced from elsewhere and prey on the bee eggs, larvae, and pupae. Seven species of Hylaeus are considered “critically imperiled and possibly extinct,” according to the Xerces Society.

Photo by Tom Murray via Bugguide.net

Because the female bees collect so little pollen, it has been problematic to determine which species are generalist pollinators, and which are specialists. Recording which flowers the females visit has only provided a little insight. Analysis of pollen grains in the larval feces of three species in Michigan revealed that pollen foraging skews toward members of the Rosaceae when those flowers are available, and Asteraceae otherwise (Scott, 1996). The western U.S. species H. bisinuatus apparently visits White Sweetclover, Melilotus alba exclusively, even when other flowers are available. The Australian species H. alcyoneus visits only Banksia flowers. Still, the vast majority of species are assumed to be generalist pollinators.

Masked bees will readily nest in artificial bee boxes, be they bundles of thin straws, sumac twigs, or blocks with small diameter holes drilled into them. Consider constructing one of these and hanging it on a south-facing exterior wall, tree trunk, or similar situation. Be sure to include a “roof” to protect the entrance holes from rain, and elevate it at least three feet from the ground. Many websites exist with further hints on how to build such nest boxes.

Lastly, don’t fret if you can’t always tell the difference between masked bees and wasps. There are records whereby species of Hyleaus were originally described as wasps by scientists.

Sources: Scott, Virginia, 1996. “Pollen Selection by Three Species of Hylaeus in Michigan,” J Kans Entomol Soc 69(4): 195-200.
The Great Sunflower Project
”Aculeata Agonistes: Yellow-faced Bees”

Spider Sunday: Ebo Time

2012-01-15T06:00:00.000-08:00

Sorry, in the wake of the popular mania over Tim Tebow, quarterback of the Denver Broncos NFL team, I could not resist the play on words. The spiders of the genus Ebo, members of the “running crab spider” family Philodromidae, are not known for their ability to score touchdowns or inspire a nation. That does not make them any less interesting as a topic of conversation, though.

Philodromids are identified rather easily by the fact that their second pair of legs is longest. The genus Ebo takes this to an extreme, as that second leg is at least twice as long as all the others. Their “wingspan” must be the greatest for their size of any spider in North America. Their body size is small, averaging between two and six millimeters depending on the species, and skewing towards the lower end of that spectrum.

There were 22 recognized species of Ebo found in North America, but some species have recently been reassigned to the genus Titanebo, leaving just seven North American species in Ebo sensu stricto. Their collective distribution is throughout the U.S. and extreme southern Canada. Other species occur in Mexico, Argentina, India, and Russia. They reach their greatest diversity in the southwest U.S., which is where I found the specimen shown in the images below. It was on the edge of the bathtub in my Tucson, Arizona apartment. I guess I cannot say for certain now whether this is an Ebo or Titanebo.

I originally posted these images on Bugguide.net, a bit reluctantly since they also showed a fair amount of lint on the bathtub. Fellow contributor Carol Davis put me immediately at ease with her own comment: “Cleanliness leads to buglessness and then what have you got? No photos!” Fair point, and I replied that I am not a messy housekeeper, I’m promoting biodiversity!

Like most running crab spiders, Ebo prowls for prey among grasses and foliage. At least two species frequent pecan groves in Texas, affording natural pest control to at least a minor degree (Calixto, et al. 2004).

What about the origin of the name, you ask? Well, the German arachnologist Eugen von Keyserling who created the genus gives no indication of its derivation. Ebo was apparently a common name in medieval Germany, a diminutive of “Ebur,” meaning “prince” or “lord.” Hm-m-m, seems that both Ebo and Tebow could qualify for that definition.

Do keep an eye out for these unique spiders, which should be easy to recognize. You could say that Ebo is all elbows.

Sources: Calixto, Alejandro, Allen Dean and Marvin Harris. 2004. Spiders in Pecans. College Station: Texas A & M University.
Kaston, B. J. 1978. How to Know the Spiders 3rd Edition. Dubuque, Iowa: Wm. C. Brown Company Publishers. 272 pp.
Platnick, Norman I. 2012. The World Spider Catalog, Version 12.5
Ubick, D., P. Paquin, P. E. Cushing, and V. Roth (eds.) 2005. Spiders of North America: an identification manual. American Arachnological Society. 377 pp.

Wasp Wednesday: Clitemnestra bipunctata

2012-01-11T06:00:00.000-08:00

Most species of insects are smaller than you would imagine. This is also true of wasps. For every species you notice, there are dozens you don’t. One common species that is easily overlooked is Clitemnestra bipunctata in the family Crabronidae.

At about 5-6 millimeters in body length, this wasp usually escapes notice. I have found them most commonly around aphid colonies where they lap up the aphids’ liquid waste, known as “honeydew.” The species ranges across most of the United States and is also recorded from Cuba.

When not living the luxurious lifestyle sipping sugary liquids, the female wasps hunt a variety of planthoppers, leafhoppers, treehoppers, and psyllids. The long list of recorded hosts (424 prey records from Cuba alone) includes Coelidia olitoria, Colladonus clitellarius, Japananus hyalinus (pictured below), Macrosteles fascifrons, Orientus ishidae, Paraphlepsius irroratus, and Prescottia lobata from the leafhopper family Cicadellidae.

Also found in excavated nests were the spittlebugs Clastoptera obtusus, Philaenus leucophthalmus, and P. lineatus; the treehopper Cyrtolobus acutus; and various members of the families Cixiidae, Dictyopharidae, Flatidae, Tropiduchidae, and Psyllidae. The wasps generally select adult hoppers much more often than nymphs.

Nests are burrows usually dug in bare soil near the top of vertical banks, and to a depth of 9-20 centimeters. One to three cells usually branch from the main tunnel. Each cell measures about six by ten millimeters, and the wasp stores 6-18 paralyzed prey per cell.

The satellite flies Phrosinella aurifacies and Metopia argyrocephala are reported as parasites of nests. The adult female flies enter the burrows and deposit live larvae inside. The larvae feed on the paralyzed prey, but often destroy the wasp egg or larvae as well. Adults of Climnestra bipunctata are preyed on by adults of the robber fly Diogmites angustipennis, and probably other predatory insects as well.

Note that this species was formerly known as Ochleroptera bipunctata, but that genus was merged with Clitemnestra by Bohart in 2000.

Sources: Evans, Howard E. and Kevin M. O’Neill. 2007. The Sand Wasps: Natural History and Behavior. Cambridge: Harvard University Press. 340 pp.
Evans, Howard E. 1968. The Comparative Ethology and Evolution of the Sand Wasps. Cambridge: Harvard University Press. 526 pp.
Bohart, R. M. and A. S. Menke. 1976. Sphecid Wasps of the World. Berkeley: University of California Press. 695 pp.

Spider Sunday: Gray Wall Jumper

2012-01-08T06:00:00.000-08:00

Few arachnologists would argue that the most charismatic of spiders are the jumping spiders, family Salticidae. These agile hunters are about as “cute” as spiders can get. They have surprisingly acute vision, and will turn to look at you with one pair of enormous eyes when you approach them. Jumping spiders can also be very colorful. Few species are immediately recognizable, however, due to their great variability in color and pattern, and their generally small size. One species that is fairly identifiable is the Gray Wall Jumper, Menemerus bivittatus.

I was fortunate to encounter several pairs of this species living up to its common name on the exterior walls of the visitor center at Bentsen-Rio Grande Valley State Park in Mission, Texas in June, 2010. The Gray Wall Jumper is not native to North America, however, having been introduced from the Old World tropics. Here in the U.S. it is generally confined to Florida, Texas, and southern California.

Jumping spiders, and hunting spiders in general, differ from web-building spiders in that both genders are nearly identical in size. Female Gray Wall Jumpers (image above) are 8-10 millimeters in body length at maturity, whereas males (images at top and below) are 8-9 millimeters. The striking differences are in their color pattern. The male has more or less a reverse color pattern from the female, at least on the abdomen. I initially thought I had taken images of two different species.

A flat, vertical surface seems an odd “habitat” for any organism, but Menemerus makes the most of it. The spiders actively stalk small flies that bask in such situations, or that are attracted to lights at night. They are strong enough to bring down fairly large crane flies, and subdue something the size of a house fly, too.

One can’t help but become enamored with these spiders, especially after seeing them in action. This video gives you just a glimpse of their behavior. See if you can identify the males and females in that clip.

The female spider constructs a lens-shaped egg sac to hold 25-40 eggs. She guards the sac inside a silken retreat that is about 1.5 centimeters in diameter. She’ll also protect the spiderlings after they emerge, for a total of roughly three weeks from egg-laying to dispersal of her offspring.

In places where their respective ranges overlap (Texas), the Gray Wall Jumper may be mistaken for the species Platycryptus undatus, shown below, or vice versa. Both are likely to be encountered on vertical surfaces such as outside walls, and they are very similar in size and markings. Platycryptus is native, however, and has a much more extensive range, extending far to the north into southern Canada.

Be sure to look for the Gray Wall Jumping Spider in your travels abroad, too. It is essentially cosmopolitan in tropical and subtropical regions throughout the world, including Japan, India, Thailand, Paraguay, and even the Galapagos Islands.

Sources: G. B. Edwards, Jr. 2002. Featured Creatures: Jumping Spiders, University of Florida (Gainesville).
Arachne.org.au

Wasp Wednesday: Recent Mentors

2012-01-04T06:00:00.000-08:00

I suppose that “recent” is a relative term, but I am delighted to report that the following gentlemen are all still alive and continuing to make very valuable contributions to science. They inspire me and make me a better entomologist and writer.

Arnold Menke, Eric Grissell, myself, Justin Schmidt

I was privileged to have the opportunity to work on a private contract to help curate the national butterfly collection at the National Museum of Natural History (Smithsonian) in April and May of 1986, where I got to meet two fine scholars working there on behalf of the USDA’s Agricultural Research Service. Dr. Arnold Menke is a world authority on wasps, especially the thread-waisted wasps in the genus Ammophila. He currently has nearly all my specimens of that genus, in fact, as he is working on a much-needed revision of those caterpillar hunters. He retired to Bisbee, Arizona in the 1990s where he also enjoys railroad history and photography.

Dr. Edward Eric Grissell (he goes by “Eric,” too, which can cause confusion at Arnold’s annual hamburger roast) is an expert on tiny parasitic wasps in the suborder Chalcidoidea. Since many of those wasps are enemies of agricultural pests, Eric was a very busy man figuring out which species could help control food-destroying insects. Today, Eric is also “retired,” but writes full-time about insects and gardening. He has produced several outstanding popular books including Thyme on my Hands, Insects and Gardens: in Pursuit of a Garden Ecology, and Bees, Wasps, and Ants: The Indispensable Role of Hymenoptera in Gardens, all published by Timber Press.

Another remarkable individual is Justin Schmidt, known famously as the “King of Sting” for his exploits in assessing the effects of insect and arachnid venoms on willing human subjects, but mostly himself. He created the “Schmidt Sting Pain Index” to quantify and describe (in prose usually reserved for connoisseurs of wine) the type of pain inflicted by stinging insects. He worked for many years at the federal Carl Hayden Bee Research Center in Tucson, before deciding to pursue his own projects full time. I greatly admire his endless curiosity, and ability to devise experiments to divine answers to his questions.

Matthias Buck

Last, but certainly not least, is Dr. Matthias Buck, currently the Assistant Curator of Invertebrate Zoology at the Royal Alberta Museum in Edmonton. I first met him online as I recall, since he freely shares his expertise on Bugguide.net. Eventually we met in person at a meeting of the Entomological Collections Network. His specialty is vespid wasps, which includes the yellowjackets, hornets, paper wasps, mason wasps and potter wasps. One of his most amazing projects is the co-creation of the Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the Northeastern Nearctic Region, along with Stephen A. Marshall and David K. B. Cheung. Matthias has all my Polistes paper wasps, and has already found examples of an undescribed species among them.

I can honestly say that it is an honor to know these men both as scientists and human beings. I will be forever grateful to them for sharing their knowledge and encouraging me along the path that I have chosen.

Spider Sunday: Thieves and Hangers-on

2012-01-01T06:00:00.000-08:00

Not all enemies of spiders kill them. Some will steal a meal. Others aren’t really enemies, but escape their own enemies by hiding out on spider webs.

While in Massachusetts, I was lucky enough to witness a common scorpionfly, Panorpa acuta, scavenging prey in the web of a sheetweb-weaver (family Linyphiidae). The spider tried to chase off the pesky mecopteran, as evidenced by the image below.

Common scorpionflies are in the family Panorpidae, order Mecoptera. They are named for the enlarged claspers of the male, part of his external genitalia. They are so large that the male must curl the end of his abdomen, giving him the appearance of a scorpion. The “long face,” terminating in chewing mandibles, also helps to identify these insects.

They go through complete metamorphosis, the larvae living in soil and leaf litter on the forest floor where they also scavenge on dead or dying, soft-bodied insects. They go through four instars (the intervals between molts), before pupating in an earthen chamber in the soil.

Another phenomenon I saw in Massachusetts was the use of spider webs as roosting places for a certain species of gall midge, family Cecidomyiidae. Gall midges are a type of fly. Whereas most flies become tangled in spider webs and eventually a meal for the spider, these tiny flies are able to select the non-sticky foundation threads of spider webs and safely suspend themselves from them. Predators of the flies, if they even managed to notice them, would risk becoming tangled in the spider web should they attempt to catch one of the diminutive midges.

This trapeze act is apparently a widespread phenomenon in the Cecidomyiidae, especially in the subfamilies Porricondylinae and Cecidomyiinae. The behavior was first reported (published) in 1853 by Johannes Winnertz.

Sources: Byers, George W. 2002. “Scorpionflies, Hangingflies, and Other Mecoptera,” Kansas School Naturalist. 48(1): 1-15.
Gagne, Raymond J. 1989. ”Family Cecidomyiidae” in Catalog of the Diptera of Australasia and Oceania, Neal L. Evenhuis, editor. Honolulu, HI: Bishop Museum & E. J. Brill. 1155 pp..

Wasp Wednesday: Early Mentors

2011-12-28T06:00:00.000-08:00

I may have started collecting wasps because no one could call me a sissy for catching something that can fight back, but I owe my continued fascination with these insects to a number of amazing mentors who showed me there is much more to hymenopterans than I ever imagined.

One of the entomologists I most admire is the late Howard Ensign Evans. Not only was he a world-class authority on Hymenoptera, but one of the most eloquent writers and “popularizers” of entomology that I have ever read. His classic Life on a Little-Known Planet is without a doubt the best introduction to insects for a general audience as has ever been published. Evans managed to maintain a passion for, and awe of, the natural world untarnished by the efforts of academia to reduce all to “models,” statistics, and biochemical reactions.

I also read Evans’ Wasp Farm, and The Pleasures of Entomology. His book Wasps, co-authored with Mary Jane West-Eberhard, was my wasp bible for many years. Mary Jane wrote an amazing and comprehensive biography of Dr. Evans that does his contributions to science and literature vastly more justice than I ever could here.

I will always treasure a piece of correspondence I received from Dr. Evans in January of 1984 after I had written him for advice on how to make a living writing. He suggested that I would need “another means of support.” His sense of humor is another admirable quality.

Just last month I picked up Evans’ A Naturalist’s Years in the Rocky Mountains, which should serve me well in getting to know the fauna, flora, and seasons of my new Colorado Springs home.

Once I got to college at Oregon State University, I had the good fortune to become acquainted with Dr. George R. Ferguson. He was a taxonomist of the highest degree, working mostly on the genera Cerceris and Eucerceris, finishing what his friend and colleague the late Herm Scullen had started. Dr. Ferguson still found time to take me under his wing, providing many identifications for my growing collection.

I’ll never forget the time I eagerly presented a small series of metallic blue sphecid wasps for his appraisal. He took a quick look and determined they were the Blue Mud Dauber, Chalybion californicum. I sighed and said that I thought they were the Steel Blue Cricket Hunter, Chlorion aerarium. He plucked out one specimen, stuck it under his microscope, and replied “Well, I’ll be, you’re right. They’re awful small, though.” He was right, too: they were males, and not particularly impressive examples of that gender, either.

Dr. Ferguson has since passed away as well, but I am delighted to report that his legacy lives on in the form of an endowment fund at OSU, which grants funding annually to outstanding undergrad and graduate students majoring in entomology there. I would expect nothing less from my most kind and generous mentor.

More than what these two men taught me about Hymenoptera was what they taught me about being a man and a human being. I hope I can be half as courteous and helpful to those who ask for my help. I hope I can be a positive and inspirational example to the students and scholars of tomorrow.

Spider Sunday: Spider Enemies

2011-12-25T06:00:00.000-08:00

Spiders may seem invincible, especially to those who fear them. Not true. Spiders are under constant threat from predators, parasites, and other mortality factors. It is impossible to even list all the agents that kill spiders, but some creatures that prey exclusively on spiders, or nearly so, are worth investigating.

Even tarantulas, the largest spiders, are not immune to attack. Enormous wasps in the genus Pepsis aggressively seek these gargantuan arachnids. Only the female wasp is armed with a stinger, a formidable weapon to match the spider’s fangs.

In the southwest U.S., the wasp fuels her superhero lifestyle on nectar, especially from milkweed flowers. Once juiced-up, she scours the ground for signs of her prey. Encountering an inhabited burrow, she lures the spider out of it and the battle begins. Tarantulas can move fast when they have to, but the wasp is usually quicker. She stings it in a nerve center on the underside of its cephalothorax, rendering the arachnid almost instantly paralyzed.

Once she has immobilized the spider, the wasp drags her victim to a hole where she caches it. She sometimes uses the spider’s own burrow. She lays a single egg on the spider, then leaves. She will repeat the process until she dies. The larva that hatches from the egg consumes the still-living spider, eventually pupating and emerging as an adult wasp the following year.

All wasps in the family Pompilidae, including Pepsis, are dedicated spider-slayers. So are mud daubers in the families Sphecidae and Crabronidae. The Black and Yellow Mud Dauber, Sceliphron caementarium, builds clod-like mud nests under the eaves of houses and other buildings, stocking each cell with numerous spider victims. The wasps are generalist hunters and almost any kind of spider will do. The Blue Mud Dauber, Chalybion californicum, is famous for killing black widow spiders, but it is also a generalist. It uses the old nests of the Black and Yellow Mud Dauber instead of building a nest from scratch.

Still other wasps don’t bother making a nest at all. The ichneumon Acrotaphus wiltii (above) simply locates a host (the orb weaver Neoscona arabesca in this case), stings it into brief paralysis, and lays a single egg on it. The wasp leaves, but her larval offspring will feed as an external parasite on the spider.

Flies are the quintessential victims of spiders, but some turn the table. Small-headed flies of the family Acroceridae, are parasites of spiders, especially trapdoor spiders.

The female fly lays hundreds or thousands of eggs, scattering them throughout the landscape. The larvae that hatch are highly mobile, host-seeking missles. Upon contacting a spider, the larva climbs up its host’s leg and burrows into the spider’s body wall. It takes up residence around the book lungs, feeding internally on its host.

A similar scenario is played out by members of the family Mantispidae, order Neuroptera. Females lay large numbers of eggs and the larvae emerge to go in search of spiders. Instead of eating the spider, they simply climb aboard and wait. What are they waiting for, you ask? A larva waits for a female spider to spin her egg sac, at which point it climbs inside and becomes wrapped up with the eggs. Then it eats the eggs, pupates, and eventually emerges as an adult mantispid. What if a larva climbs onto a male spider? It will transfer to a female during mating.

Among the most amazing spider predators are “helicopter damselflies” of the family Pseudostigmatidae.

These tropical giants hover in front of a spider web and simply pluck the owner off its silken platform. They are aquatic as nymphs, living in pools of water inside treeholes and preying on other small animals.

It should come as no surprise that perhaps the most lethal spider predators are…other spiders. Spiders may be able to negotiate their own webs, but can easily become entangled in another spider’s snare. Further, mating is risky business, even if you are not a black widow. Female spiders are usually larger and more powerful than their mates, and may eat potential suitors instead of courting them.

No spider hunter, however, matches the skill and stealth of the jumping spiders of the genus Portia, found in Africa, Asia, and Australia. They may build their own webs, unusual for jumping spiders, or actively stalk other kinds of spiders in their webs. Even other jumping spiders are a potential meal.

Have you ever seen a spider as the victim of another animal? Did it surprise you? Please feel free to share your stories here. I may also revisit this topic to address other spider-eating creatures.

Aknowledgements: Acrotaphus wiltii image by Tom Murray in Massachusetts and borrowed from Bugguide.net; Acrocerid fly image is of Eulonchus tristis, taken in Washington state by Stephen Hart and borrowed from Bugguide.net; Portia spider image taken from sgmacro, by Nicky Bay of Singapore; all other images by Eric R. Eaton unless otherwise noted.

Wasp Wednesday: Caliadurgus hyalinatus

2011-12-21T15:21:00.000-08:00

The members of the wasp family Pompilidae are known as “spider wasps” because the adult females hunt spiders as food for their larval offspring. The elegant little species Caliadurgus hyalinatus is no exception. I found it to be quite common in Cincinnati, Ohio when I lived there and collected insects. It was like finding an old friend when my girlfriend Heidi Genter pointed out this specimen on goldenrod at Cape May Point State Park in New Jersey on October 18, 2010.

This wasp was formerly known as Calicurgus hyalinatus. Henry Townes, in his monograph Nearctic Wasps of the Subfamilies Pepsinae and Ceropalinae separated the species into four subspecies. Collectively, they range over most of the eastern U.S. and and adjacent Canada, west to Washington state, the Dakotas, and Kansas, south to Georgia and Louisiana with sparse records in Texas, New Mexico, and Arizona. This is also a holarctic species, found in Europe as well.

The famed French entomologist Jean Henri Fabre documented his observations of the species in Europe in More Hunting Wasp. Here in the U.S., Howard E. Evans and Frank E. Kurczewski have contributed to our understanding of this species in the New World. Information from their papers is presented in the following paragraphs.

C. hyalinatus apparently chooses only orb weavers of the family Araneidae to feed its offspring. Host records include the Starbellied Orb Weaver, Acanthepeira stellata, one of the furrow spiders, Larinoides patagiatus, the Humpbacked Orb Weaver, Eustala anastera, the Marbled Orb Weaver, Araneus marmoreus, and a species of Neoscona. The prey was an immature spider in every instance, not surprising given that this small spider wasp could not overpower mature orb weavers, many of which are quite large. The wasp must sting the spider into paralysis to facilitate its “cooperation” in being carted off by the wasp to the nest site.

The female wasp grasps her immobilized victim at the base of a leg, and then walks forward with the prey held in front of her. She may also climb a vertical object and fly (or at least glide) from it to achieve greater distance with more minimal effort. Once she arrives in a suitable spot she stashes the spider in a crotch in vegetation near the ground, and begins to excavate a burrow.

The wasp can work quickly in sandy soil, completing her simple burrow in about thirty minutes. She eventually surfaces, grabs her spider, and tows it underground. The tunnel is diagonal, about four centimeters in length, and terminates in a centimeter-long cell about four centimeters below the surface. The spider is left in the cell, on its “stomach,” with a single egg attached. The wasp then fill in the entrance to the burrow and begins the process anew.

Caliadurgus hyalinatus is not easily confused with any other spider wasp in North America. Females have clear wings with a dark spot on each front wing, a bicolored abdomen, and bicolored hind legs. The hind tibia has a noticeable row of teeth along the upper edge.

Sources: Evans, Howard E. and Carl M. Yoshimoto. 1962. “The Ecology and Nesting Behavior of the Pompilidae (Hymenoptera) of the Northeastern United States,” Miscellaneous Publications of the Entomological Society of America 3(3): 67-119.
Kurczewski, Frank E. and Edmund J. 1968. “Host Records for Some North American Pompilidae (Hymenoptera) With a Discussion of Factors in Prey Selection,” Journal of the Kansas Entomological Society 41: 1-33.

Spider Sunday: Tinus peregrinus

2011-12-18T06:00:00.000-08:00

Nursery web spiders of the family Pisauridae are more diverse than I thought. I had been under the impression that there were only two genera in North America: Pisaurina and Dolomedes. Turns out there is another: Tinus. Thanks to Lynette Schimming at Bugguide.net, I found out that what I thought were immature fishing spiders I had observed in Tucson, Arizona and Mission, Texas were actually adults of Tinus peregrinus.

Whereas most adult fishing spiders and nursery web spiders are quite large (body length 10-28 mm), Tinus peregrinus maxes out at around 10 millimeters body length, males a millimeter shorter still.

This species ranges across the southwest U.S. from southern California to the southern tip of Nevada, and east to Texas and Missouri. It also occurs in northern Mexico. The “type locality,” the site where the first known specimen was collected, is listed as Hot Springs, Arkansas, but it is suspected that this is in error.

Virtually nothing is known of the life history and biology of this animal. Egg sacs in preserved collections are dated late July and early August. I have observed this species under bark on trees near the edges of ponds, and also at the edges of window frames. It would appear that once an individual spider finds a location that suits it, the spider stays put. One specimen I found in the corner of a window had several shed exoskeletons in its web, suggesting it had resided there for some time. No wonder, the web was also full of tiny midges (flies in the family Chironomidae) that had swarmed the lighted building at night.

Like most spiders in the Pisauridae, T. peregrinus appears to prefer the vertical plane, rarely found on the ground.

Sources: Carico, James E. 1976. “The Spider Genus Tinus (Pisauridae),” Psyche 83: 63-78
Kaston, B. J. 1978. How to Know the Spiders (Third Edition). Dubuque, Iowa: Wm. C. Brown Company Publishers. 272 pp.

Wasp Wednesday: Polistes flavus

2011-12-14T06:00:00.000-08:00

One of the most conspicuous wasps in the Sonoran Desert is the paper wasp Polistes flavus. This is a large wasp that frequents the same narrow belt as saguaro cacti, seldom being encountered at lower or higher elevations. Its large size, and almost entirely bright yellow color helps to separate this species from every other paper wasp in the region.

Little is known about P. flavus despite its relative, if seemingly localized, abundance. I have seen nests on only a handful of occasions, and they were all placed under the eaves of buildings. Unfortunately, those observations were made before I started taking digital images. I do recall that the nests were large, if only because the paper cells needed to accommodate these wasps have to be correspondingly large. Fortunately, my good friend Margarethe Brummermann did manage an image or two, one of which is shown below.

You are most likely to see these wasps in one of three situations: at water, at flowers, and perching on prominent vegetation. Worker females often congregate around receding waters of the intermittent streams characteristic of the Sonoran Desert. They may even land on the water, sprawling across the surface film and drinking deeply. They will visit swimming pools when natural sources are not available. Many other species of desert Polistes and Mischocyttarus will exhibit the same behavior. They all need water to manufacture saliva to mix with wood fibers to create the paper used in building their nests.

Paper wasps attack caterpillars and other insects to take back to the nest to feed the growing larvae, but the adult wasps need carbs, not protein. Consequently, paper wasps make use of flower nectar and “honeydew” from aphid colonies. Look for Polistes flavus on the blossoms of Seep Willow (Baccharis salicifolia) and, to a lesser degree, Desert Broom (Baccharis sarothroides). The wasp in the image below is on a Seep Willow.

Male paper wasps are often even larger than the females and therefore even more obvious and intimidating. This is especially true when they engage in territorial behavior, perching on prominent twigs or branches along the edges of dry riverbeds and other flyways. From these outposts the males scan for passing females and rival males. They will also chase away other insects, then return to their perch or another perch close by. Males do not have stingers, but are powerful enough to back up their threats.

How do you tell a male paper wasp from a female? Males have longer antennae, dramatically hooked at the tip, and their faces are more “square” than those of females. Males tend to have very pale faces, too. Females have shorter antennae, not as prominently hooked, and triangular faces that are usually darker.

One paper wasp likely to be confused with P. flavus is P. apachus, which is colored in yellow and reddish brown. P. apachus almost invariably has two parallel yellow stripes on the top of the thorax (see below), whereas that area is almost entirely yellow in P. flavus. Another confusing species is P. aurifer, which is entirely reddish brown on top of the thorax.

Look for P. flavus in Arizona, as well as southern California, Nevada, Utah, New Mexico, and western Texas. Males can easily overwinter in milder parts of that range, though they are normally more common in autumn as colonies prepare to suspend activities for the colder months.

Spider Sunday: Bowl & Doily Spider

2011-12-11T09:06:00.000-08:00

You don’t have to see a Bowl and Doily Spider, Frontinella communis, to recognize it immediately. The name says it all. Its web looks exactly like a bowl atop a “doily,” or saucer. It may be the most recognizable web outside of an orb web.

The Bowl and Doily spider is also one of the most common and widespread spiders in North America. The spider itself is not terribly impressive, mature females measuring only 3-4 millimeters in body length, and males slightly smaller. They are handsomely and boldly marked with black and white stripes on the abdomen, a brown cephalothorax, and brownish legs.

The webs are only a few inches across, and usually well off the ground, stretched between twigs, suspended from fences, and other objects. The spider hangs upside down on the bottom of the “bowl,” presumably awaiting prey to literally “drop in” for dinner. A tangled scaffold of silk lines suspends the bowl, and insects are likely to hit one of the threads and be caught by the upturned sheet below. At least one reference asserts that the spider pulls its prey through the bottom of the “bowl” and then retires to the “doily” to dine.

Another species in this genus, F. huachuca, is known from Arizona. I am wondering if the specimen I imaged in the Chiricahua Mountains at Onion Saddle (picture below) belongs to that species.

Bowl and Doily spiders are not only common, but locally abundant. Find one web and you will likely find dozens of others in close proximity. This may help facilitate mating. Males can be seen sharing the webs of females in late summer and fall.

Look for this species at forest edges and in pine woodlands especially, though it is just as likely to turn up in your yard, garden, or orchard. Note that earlier references treat the species as Frontinella pyramitela.

Wasp Wednesday: Not Wasp V

2011-12-07T10:27:00.000-08:00

This is the fifth installment of “Wasp Wednesday” that treats another kind of insect often mistaken for a wasp. Today we entertain the clearwing moths of the family Sesiidae. Yes, some moths can pass for wasps!

My own experience suggests that sesiids are not terribly common. I have few in my collection and have not often observed them in the wild. Still, at least a few species are abundant enough to be considered pests, with much research devoted to their control, including the production of synthetic pheromones designed to trap adult moths. More on that later.

You are much more likely to see the moths than you are their larvae. The caterpillars of sesiids are borers, so are concealed in stems, roots, vines, or tree trunks for the entirety of their immature lives. You might be lucky enough to see where a caterpillar had been living because the molted pupa skin often protrudes from a hole where the moth exits.

They may be scarce, but clearwing moths are certainly diverse. There are over 1,100 species known (so far), in 120 genera. The narrow forewings, nearly devoid of scales except for the veins and wing margins, are characteristic. The front wings and hind wings connect in the manner of most moths, with a hook-like “frenulum” on the leading edge of the base of the hind wing interfacing with a patch of setae (hairs) on the underside of the forewing, called a “retinaculum.” However, there is also a unique series of scales on each wing that interlock with each other, further securing the wing coupling.

As you would expect, sesiid moths fly during the day, and one is most likely to find these mimics at flowers where they mingle seamlessly with their “models,” real wasps and bees.

I was fortunate enough to spy the orange-and-black specimen above as it flitted about an open field in Colorado Springs, Colorado on October 22, 2011. Euhagena nebraskae (no common English name, sorry) is one of those “clearwings” that actually does have an abundance of scales on the wings. The larvae of this species are known to bore in the roots of evening primrose (Oenothera spp.). It flies in the fall as an adult moth, and the species is known from southern Alberta to Mexico City, west to southern California. My friend Ted MacRae wrote a post on this species in his blog ”Beetles in the Bush”. My guess is that E. nebraskae mimics some kind of small spider wasp in the family Pompilidae.

I found another interesting sesiid back on August 1, 2009 in South Deerfield, Massachusetts. Contrary to its name, the Lesser Peachtree Borer, Synanthedon pictipes, feeds mostly under the bark of wild cherry. The caterpillars seem to prefer areas of the trees malformed from mechanical injuries, fungal infections, or other abnormalities. The adult moths are convincing mimics of a variety of wasps that share a black-and-white color pattern.

Pest species like the Lesser Peachtree Borer require monitoring in orchards where they can be problematic to census by simple observation. Consequently, during the 1970s, efforts were made to create synthetic pheromones (sex scents produced by the female moths to attract mates in this case). This strategy has paid off, and continues to do so. The only drawback has been the notorious persistence of the pheromones, even after washing and cleaning. Many an agricultural entomologist has been embarrassed in public by an entourage of eager male clearwing moths still sensing residual artificial pheromones on his or her person.

Despite the risk of ridicule, I am sorely tempted to purchase a variety of synthetic pheromones if it will result in more photo ops with these remarkable, beautiful insects. I would sure like to see another Glorious Squash Vine Borer, Melittia gloriosa, for example, like the one below from Pima Canyon in Arizona, August 29, 2010.

Sources: Covell, Charles V. Jr. 1984. A Field Guide to Moths of Eastern North America (Peterson Field Guide Series). Boston: Houghton Mifflin Company. 496 pp.
Powell, Jerry A. and Paul A. Opler. 2009. Moths of Western North America. Berkeley: University of California Press. 370 pp.
Moth Photographers Group
San Diego Natural History Museum
”Using Pheromones to Attract Clearwings”.

Spider Sunday: Spiders and Celebrities

2011-12-04T06:00:00.000-08:00

Nobody has a neutral reaction to spiders, so it comes as no surprise that celebrities find themselves on one side of the fence or the other regarding their affection or disdain for the arachnid world.

Humorist David Sedaris has a fascination with the Giant House Spider, Tegenaria duellica. He wrote about them in the essay “April in Paris” in the book When You Are Engulfed in Flames. “April” is the name of one of the spiders that the author found inside his home in Normandy, France. He fed her flies and watched her behavior on his windowsill. He became so enamored that (in the essay at least) he took her to Paris to see the Eiffel Tower.

Actor Jim Parsons of The Big Bang Theory on CBS television pretended to be scared of spiders when he presented the word “arachnid” on an episode of Sesame Street. His real-life reaction is much more admirable: “….I’m not terribly afraid of them. I have a lot in my house, but I try not to kill them. I just shuffle them outside with a piece of paper.”

Dominic Monaghan of Lost fame is incredibly spider-friendly. He was set to join an expedition two or three years ago to re-discover an African tarantula, Hysterocrates hercules, known currently only from a museum specimen collected in Nigeria in the late 1890s (its description published in 1899). I had the pleasure of briefly meeting Mr. Monaghan at the annual “Bug Fair” in Los Angeles last May. He told me that the mission had yet to take place but that he was still optimistic that it would happen.

The spider-celebrity connection works the other way, too. Several recently-described species have been named after contemporary celebrities. Pachygnatha zappa immortalizes legendary rocker Frank Zappa. The species was collected on Mount Cameroon in Africa.

The North American trapdoor spider genus Aptostichus has species named after Angelina Jolie and Stephen Colbert. Jason Bond, the scientist and professor at East Carolina University who named these spiders also christened another trapdoor spider after Canadian musician Neil Young.

I hope that the celebrities feel honored to have arachnids bearing their namesakes. I know that I feel honored when I find arachnophiles anywhere, celebrities or not.

Wasp Wednesday: Gall Wasps

2011-11-30T06:00:00.000-08:00

Evidence of the activities of wasps can be found even when the insects themselves are long gone. Their mud or paper nests remain affixed to branches, and beneath the eaves of our homes. Sometimes, however, those nests are not recognizable as such. Plant galls are one example of this.

Many types of organisms can create galls. Flies, aphids, adelgids, mites, nematode worms, bacteria, viruses, and even fungi can stimulate abnormal plant growth, but the gall wasps of the family Cynipidae are perhaps the most common culprits. There are nearly 2,500 species worldwide, more than 750 of those occurring north of Mexico. Here in North America, the overwhelming majority of gall wasps are associated with just two groups of plants: the oak family and the rose family.

Nothing about the biology of cynipids seems to be very straightforward. Most species present an “alternation of generations” life cycle as figured in the diagram below from Some Plant Galls of Illinois. The spring population is normal, with winged adults of both genders emerging and mating to create the next generation. There is also an “agamic” generation represented only by females. These insects, which typically emerge in late autumn or winter, are wingless, and capable of reproducing without insemination by males. This kind of asexual reproduction is termed “parthenogenesis,” and many insects are capable of it. I found this example of just such an agamic female gall wasp on Thanksgiving day at the Cheyenne Mountain Zoo in Colorado Springs.

The large, hard galls most obvious to us are the ones produced *by* the spring bisexual generation, and the ones from which the asexual winter generation emerges. The spring galls are soft, small, and inconspicuous, usually on buds, flowers, or young leaves of the host plant.

Chemical compounds introduced by the adult female wasp in the course of laying her eggs, and/or by the larval wasp in the course of feeding, are probably responsible for the form and size of the gall produced, stimulating the expansion of cells in the host plant’s tissues as well as the type of growth in the vicinity of the insect. One can often determine at least the genus of the wasp by examining the gall it forms and knowing the exact host plant. The gall, below, for example, is a “Mossy Rose Gall,” produced by Diplolepis rosae, a species probably introduced from Europe in the course of cultivating roses. This specimen was also imaged at the Cheyenne Mountain Zoo.

The rough oak bullet galls pictured below are solid. Here on the Front Range, three species of wasps in the genus Disholcaspis create these kinds of galls on one host plant: Gambel’s Oak (aka “Shin Oak”), Quercus gambelii. I have observed that oaks are either gall-free or nearly so, or very heavily infested.

Ironically, galls rarely cause more than mere cosmetic “damage” to the host plant. An affected tree or shrub won’t win a beauty contest, but neither is it likely to keel over.

Much remains to be learned about galls and their makers, perhaps because so many other insects exploit galls and/or parasitize gall wasp larvae. Collect a large number of galls and you are as likely to raise an assortment of parasitic wasps as you are the gall wasps you would expect. Further complicating matters, still other insects lay their eggs in galls because of the abundance of food that galls present, and their nutritional value. These “houseguests” are called “inquilines” that live off the work of the gall wasp mother, but that do not affect the survival of her offspring.

Should you decide to take up the study of gall wasps, you will be in good company. Dr. Alfred C. Kinsey (yes, that Alfred Kinsey of human sexuality fame) began his career by spending two decades studying cynipids at Indiana University. I’ll be grateful if I can identify two other types of galls that appear on Gambel’s Oak. One is a leaf gall (top image in this post), and the other is a more linear twig gall.

Sources: Winterringer, Glen S. 1961. Some Plant Galls of Illinois. Springfield: Illinois State Museum, Story of Illinois No. 12. 51 pp.

Spider Sunday: Spider Sex Ed

2011-11-27T06:00:00.000-08:00

Just to clarify, this lesson is for people, not spiders. Spiders already know how to do it. Wait, that didn’t come out right, either. What I mean is, this is a primer on how to tell spider genders apart, and show why it is so difficult to properly identify your average arachnid.

Immature spiders cannot be identified to species (sometimes not even to genus) because they lack developed external genitalia that are species-specific. It is even more complicated than that because more “primitive” types of spiders don’t have complex genitalia anyway. Tarantulas, trapdoor spiders and their allies, collectively known as the Mygalomorphae, don’t have fancy equipment.

Next up on the ladder from mygalomorphs is another large clade called Haplogynae. The term has Greek roots and roughly translates to “half woman.” Among familiar haplogyne spiders are crevice weavers (Filistatidae), recluse spiders and their kin (Sicariidae), cellar spiders (Pholcidae), and spitting spiders (Scytodidae). Mature female haplogynes have a relatively simple genital opening known as the gonopore, accessed by the male through her “epigastric furrow.” The epigastric furrow is a simple transverse slit on the underside of the female’s abdomen.

Male spiders of all species do not have a penis, so they have evolved to use their pedipalps as intromittent sex organs to transfer sperm to the female. Pedipalps are the leg-like mouthparts nearest the spider’s face. The male spider prepares himself by spinning a small sheet of silk called a “sperm web.” He then extrudes seamen onto the sheet and sucks it up into a reservoir inside each pedipalp. He is now ready to go hunting for a mate. Males always wander to find a mate, even those species normally confined to webs.

Male mygalomorph and haplogyne spiders have no need for elaborate pedipalps because the female’s genital opening is correspondingly simple. Not so with the most highly-evolved spiders, the Entelegynae. Greek for “whole woman,” the term describes the much more complex genitalia of both genders. The overwhelming majority of non-fossil spiders fall within this group.

Sperm from the male goes into the female’s oviduct during mating in haplogyne spiders; and the sperm exits the same duct when the female lays her eggs. The sperm goes in one duct (copulatory duct) and out another (fertilization duct) in entelegyne spiders. Females of all types of spiders are capable of storing sperm from one mating for use their entire reproductive lives. This storage tank is called the spermathecae.

Female entelegyne spiders usually have a sclerotized (hardened tissue) “door” to their genitalia, located on the underside of the abdomen just above the epigastric furrow. This apparatus is called an epigynum (image above). It is usually composed of two openings, such that the structure has a symmetrical appearance. It is key to identifying many spiders to genus and species that otherwise look virtually identical to other, unrelated spiders.

The epigynum is more like a “lock” to the spider itself, as only males of the same species are able to mate with her. The male’s pedipalps are correspondingly complex, the “keys” to her “lock.” Male spiders that are one molt away from adulthood are termed penultimate and their pedipalps are swollen but not completely formed. The terminal segment changes radically with that last molt.

The image above shows the ventral (underside) view of the pedipalp of a mature spider. The dark, circular line is the “embolus,” the appendage that enters the female’s epigynum. The area behind the embolus is the “bulb” in which the sperm is stored. The bulb rests inside the cup-like dorsal plate called the “cymbium.” The pedipalp can also have various processes and projections on the cymbium and/or the patella or tibia segments.

Anyone who is serious about identifying spiders will not be able to avoid journal articles and books filled with images not of whole spiders, but their genitalia. Figuring out which end is up and exactly which parts the text is describing is a lot like solving a puzzle. It can be quite rewarding. Heck, just look at all the fun I’m having.

Sources: Ubick, D., P. Paquin, P. E. Cushing, and V. Roth (eds). 2003. Spiders of North America: an identification manual. American Arachnological Society. 377 pp.

Wasp Wednesday: Ant-queen Kidnappers

2011-11-23T06:00:00.000-08:00

It is thanks to the book Big Game Hunting in the City Parks that I learned as a child of the “Ant-queen Kidnapper” wasps in the genus Aphilanthops. The captivating account by author Howard G. Smith of one of the female wasps hunting and transporting her prey was just too amazing to believe. Turns out it is a true story, just seldom witnessed.

The genus Aphilanthops, in the family Crabronidae and subfamily Philanthinae, occurs only in North America, including Mexico. There are four species, and at least two of them prey on on the winged queens of ants in the genus Formica. They can easily be mistaken for beewolf wasps in the genus Philanthus, but the inner eye margins of Aphilanthops are straight, not emarginated (notched) as they are in beewolves.

You are most likely to encounter the adult wasps as they drink nectar from flowers. The specimen of A. frigidus shown here was spotted in South Deerfield, Massachusetts in the late morning of July 19, 2009. This species ranges across much of the continent from Nova Scotia to British Columbia, and south along the major mountain ranges to the Carolinas, New Mexico and Arizona, and central California (mostly along the coast).

How the relationship between these wasps and their prey evolved is beyond me, but timing is truly everything in this case. The adult female wasp must be ready to take advantage of the short window in which ant colonies swarm. Ant colonies liberate males and new queens typically only once each year. Several ant nests must do this simultaneously to facilitate exchanges in genetic material and thus prevent inbreeding. So, the ant-queen kidnappers don’t have much time to apprehend their victims. Maybe only one day.

Each female Aphilanthops frigidus excavates her own nest burrow, usually in flat or gently sloping sandy soil. Several wasps usually nest in close proximity to one another, but whether they are actively competing for prey from the same ant nests is not obvious. The burrow descends underground at about a forty-five degree angle and terminates in a “waiting room” at 12-25 centimeters below the surface. Up to four ant queen victims are stored in the cell while the wasp constructs additional cells that will host her offspring. These “brood cells” may be 23-45 centimeters underground. Two to three ants are stored in each brood cell, a single egg laid on one of the victims. The cell is then plugged, and the wasp then addresses the next cell. Just how many brood cells are typical of a single nest is unknown. Once finished provisioning all the cells, the was fills in the burrow entrance with additional soil.

Accounts of attacks on the ant queens vary. Howard Smith reports that ant queens are attacked almost immediately upon emerging from the nest. Other observations conclude that the ants are attacked upon landing after their nuptial flights. At some point, the wasps detach the wings of their victims before storing them. The ants are flown back to the nest threshold where they are laid while the wasp inspects the interior of the burrow, then re-emerges to drag the ant down the tunnel by an antenna.

There are no observations of any species other than A. frigidus, so there is a lot to be learned in the future. The most common species I found in Arizona was A. hispidus (image above and below), which is abundant on the blossoms of Seepwillow (Baccharis salicifolia) in August and September. A. frigidus is active mostly from late June to mid-August, at least in New York state where Howard E. Evans studied that species.

Ant-queen kidnappers are not immune from their own villains, principally the “satellite flies” in the family Sarcophagidae. Senotainia trilineata is a confirmed parasite that lays its larvae (yes, the female fly “larviposits”) on the ant victims during their transport to the wasp’s burrow. Metopia leucocephala and Euaraba tergata are also prime suspects in nest failures, as they have been observed loitering in the vicinity of nest aggregations.

Consider doing your own “stake-out” at any wasp nest. Make a video if you are able. Chances are you can add to our scientific knowledge, if not make pioneering discoveries about prey and parasite relationships, seasonality, and other natural history.

Sources:Bohart, R. M. and E. E. Grissell. 1975. “California wasps of the subfamily Philanthinae (Hymenoptera: Sphecidae),” Bulletin of the California Insect Survey 19: 1-92.
Bohart, R. M. and A. S. Menke. 1976. Sphecid Wasps of the World. Berkeley: University of California Press. 695 pp.
Krombein, Karl V. and Paul D. Hurd, Jr. 1979. Catalog of Hymenoptera in America North of Mexico Vol. 2 Apocrita (Aculeata). Washington, DC: Smithsonian Institution Press. Pp. 1199-2209.
Smith, Howard G. 1969. Hunting Big Game in the City Parks. New York: Abingdon Press. 240 pp.

Spider Sunday: Coras

2011-11-20T06:00:00.000-08:00

Some spiders are so strange that they defy even experts to properly classify them. Such is the case with the genus Coras, which includes some very common species like C. medicinalis that spin funnel-like webs in and around human structures as well as natural settings.

First described by Nicholas Marcellus Hentz in 1821, C. medicinalis was placed in the genus Tegenaria. Charles Athanase Walckenaer put it in the genus Clubiona in 1837, but this move was not accepted by the bulk of his peers. So, he returned the species to the genus Tegenaria but changed the species to T. nemorensis. Hentz reasserted his intial name on two occasions, in 1847 and 1867. Eugen von Keyserling, in 1887, proposed Coelotes as the proper genus, and urbanus as the species name. Have I lost you yet? No? Good, because it gets more complicated still.

Eugene Simon published a revision of Coelotes in 1898, creating the genus Coras and resurrecting Hentz’s species name: Coras medicinalis thus achieving its currently accepted name. James Henry Emerton still broke ranks with his colleagues in 1902, assigning this species the name Tegenaria (subgenus Coelotes) medicinalis. John Henry Comstock apparently had the final word in 1912, asserting Simon’s revision as the official status for the species.

Even more astonishing, the genus Coras has bounced between families like a taxonomic pinball. Frederick Octavius Pickard-Cambridge originally placed Coras in the subfamily Coelotinae of the family Agelenidae. This genus, as well as the closely-allied genus Wadotes stayed in the Agelenidae until 1986, when Joerg Wunderlich moved them to the family Amaurobiidae. What was wrong with that, you ask? Well, one of the defining characteristics of the Amaurobiidae is the presence of an “extra” plate-like silk-spinning organ called a cribellum, located just in front of the spinnerets. The thing is, Coras and Wadotes don’t have this structure. Just this year the two genera boomeranged back to the Agelenidae, though I cannot presently find the journal article confirming this.

Thankfully, the biology of Coras is more straightforward. There are fifteen species in North America, all of them found principally east of the Mississippi River (southeast Canada south to Florida and west to Wisconsin and Louisiana). The genus can be identified in part by the eyes. The anterior median eyes are larger than the anterior lateral eyes. That means that the row of eyes nearest the jaws has the middle pair larger than the outer pair. I find the pattern of dark lines on the carapace to be fairly diagnostic as well.

Their webs are generally not as large as those of other funnel-web spiders, perhaps because the spiders themselves are not that large. Mature females average between 8 and 13 millimeters in body length, males 8-10 millimeters. Adult spiders are found in summer and fall. Egg sacs are probably produced in autumn since both adult and juvenile specimens have been observed hibernating in silken retreats under rocks during the winter months.

The webs may be well off the ground as evidenced by the one shown above. It was attached to the exterior of a pump house in Mount Sugarloaf State Reserve in South Deerfield, Massachusetts. The multiple retreats, instead of singular, is typical of the genus, too. These are spiders of forested habitats that also build their webs from beneath stones, from crevices in rock walls, and from loose bark on trees and logs. They are not strangers to basements or cellars, though, so look for them there as well.

Coras medicinalis acquired its species name from Hentz’s knowledge that the webs of this spider were used to make a tincture (alcoholic extract) for the relief of fevers back in the 1800s. Good to know we have advanced in our pharmaceuticals since then, leaving us free to simply enjoy these spiders on their own merits.

Sources: Bradley, Richard A. 2004. In Ohio’s Backyard: Spiders. Columbus, Ohio: Ohio Biological Survey Backyard Series No. 4. 185 pp.
Cates, Jerry. 2011. ”Araneae: Agelenidae: Funnel-web Spiders,” Bugs in the News. November 5, 2011.
Gaddy, L. L. 2009. Spiders of the Carolinas. Duluth, Minnesota: Kollath+Stensaas Publishing. 208 pp.
Howell, W. Mike, and Ronald L. Jenkins. 2004. Spiders of the Eastern United States. Boston: Pearson Education, Inc. 362 pp.
Levi, Herbert W. and Lorna R. 1968. Spiders and their Kin. New York: Golden Press. 160 pp.
Moulder, Bennett. 1992. A Guide to the Common Spiders of Illinois. Springfield, Illinois: Illinois State Museum Popular Science Series, Vol. X. 125 pp.
World Spider Catalog.

Wasp Wednesday: Anacrabro ocellatus

2011-11-16T06:00:00.000-08:00

You can often get a clue as to the identity of a wasp by noting what kind of prey she is toting. Ok, so this only works with female wasps, and it is largely a matter of luck to catch one in the act of subduing or transporting prey. Still, if you see a little (6-7 mm) black and yellow wasp in possession of a plant bug in the family Miridae, it is probably Anacrabro ocellatus, in North America anyway.

The funny thing about the image above is that until I uploaded it to my computer and cropped it, I thought the subject was a yellow-faced *bee* in the genus Hylaeus. I shot this by the Campus Pond on the University of Massachusetts campus in Amherst on August 6, 2009.

Anacrabro is a genus with two species north of Mexico. A. ocellatus, with two subspecies, is widespread east of the Rocky Mountains. A. boerhaviae is recorded in the extreme southwestern U.S. and in Mexico.

Most of the other genera in the tribe Crabronini, family Crabronidae, are fly-killers that use species of the order Diptera as food for their offspring. By contrast, Anacrabro seeks plant bugs in the family Miridae, order Hemiptera. Specifically, A. ocellatus hunts almost exclusively for adults of the “Tarnished Plant Bug,” Lygus lineolaris, pictured below.

Tarnished Plant Bugs are certifiable pests. They are generalist feeders that afflict over half of all cultivated plant species in the continental U.S. Substantial numbers of them can certainly cause severe damage to crops and garden plants. Thank goodness the wasp likes to stock them in the larder for her brood.

Anacrabro ocellatus is a “fossorial” wasp, meaning that the female digs a burrow in the soil for her nest. Each wasp digs a nearly vertical tunnel 9-16 centimeters deep, though the shaft may wind or loop in hard-packed soil. Short side tunnels may be present half-way down, but more typically longer side burrows diverge in various directions near the bottom of the main tunnel. Very short passages radiate from these longer side tunnels, each terminating in a single cell. It is into these chambers that 4-9 prey bugs are placed as food for a single wasp larva per cell. Each nest has from one to ten or so cells. Do the math and that makes Anacrabro a pretty heroic pest control species. Females may construct more than one nest, too.

Studies have shown that this wasp suffers relatively little from nest parasites, though in some instances the contents of the subterranean cells were preyed upon by ants. The nest entrance is often concealed by overhanging weedy vegetation, and the female wasp takes pains to disperse the excavated soil, so perhaps such strategies pay off in reduced incidences of parasitism.

Between hunting and nest-digging, females refresh themselves on flower nectar, especially at the umbels of wild carrot (aka “Queen Anne’s Lace,” Daucus carrota). They also visit goldenrod (Solidago), milkweed (Asclepias), and other flowers. That is where you are most likely to encounter them.

Besides its prey preferences, Anacrabro can be separated from very similar-looking wasps such as Ectemnius, Lestica, and Crabro by the very concave underside of the abdomen.

Sources: Bohart, R. M. and A. S. Menke. 1976. Sphecid Wasps of the World. Berkeley: University of California Press. 695 pp. (and source of the drawing above, by Judy Jay).
Kurczewski, Frank E. and David J. Peckham. 1970. “Nesting behavior of Anacrabro ocellatus ocellatus (Hymenoptera: Sphecidae),” Ann Entomol Soc Am 63(5): 1419-1424.

Spider Sunday: Spiders 'R' Us

2011-11-13T17:13:00.000-08:00

Yesterday, the people who brought you SpiderIdentification.org launched literally a “brand” new website, Spiders.us. The new website will have an expanded range of more traditional content, not the interactive forum of its predecessor. Not to worry, you can still post “mystery spiders” to the Facebook page for SpiderIdentification.

Spiders.us is dedicated to being your headquarters for everything “spider” in the United States and Canada. The aim is to be accurate above all else, for there exists so much misinformation, contradictory information, and downright myth, superstition and urban legend that it is no wonder so many people are fearful of spiders. We empathize and promise to put the squeamish and scared at ease as best we can.

We will also defend spiders for the important roles they play in nature, pest control, medicine, engineering and other economic and cultural realms. Here you will find:

Help in identifying the “mystery spider,” or even its web, in your home, office, yard, or garden.
Help in avoiding and preventing spider bites.
The latest news on spiders from the scientific community.
Educational resources from online articles to scientific papers.
Articles on the positive impacts of spiders on human culture.

We also look forward to hearing from you about how we can make this website more user-friendly and comprehensive. While we see our audience as people with little or no prior knowledge of the arachnid world, you will also find material that is more sophisticated, suitable for naturalists, librarians, teachers, and even scholars.

I am personally looking forward to this new venture, creating content for the site and learning new things myself along the way. Won’t you join me?

Wasp Wednesday: Passaloecus

2011-11-09T16:45:00.000-08:00

I am still learning the very basics of taking images of insects, like using a flash even when it doesn’t look like I need to. Therefore, I have only one respectable image of a live specimen of one of my favorite wasps, in the genus Passaloecus. They are predators of aphids, but are themselves pretty small, averaging 6-8 millimeters in body length.

Besides carting aphids back to their nests as food for their larval offspring, the female wasps feed on “honeydew,” the sweet liquid waste product secreted by aphids in copious amounts. Wasps of all kinds eagerly lap up the sticky fluid from the surface of leaves. That is how I was able to get the image above, on the leaf of a young aspen tree at the Cheyenne Mountain Zoo in Colorado Springs on July 13, 2011.

The genus Passaloecus, pronounced Pass-uh-LEE-kus, is in the wasp family Crabronidae, subfamily Pemphredoninae. There are approximately sixteen species of Passaloecus in North America, collectively found across the entire continent. While they are small and relatively non-descript black insects, I find I can recognize them fairly easily by their white or ivory jaws.

These are solitary wasps that you can actively attract to your yard by providing artificial nests for them. They nest in pre-existing beetle borings, and/or hollow stems and twigs, and vacant galls which they partition into a linear series of cells. As their habitat gets converted to subdivisions and dead, standing trees are preemptively felled to avoid lawsuits, these wasps face a real estate shortage. Simply drilling holes about 3/16th of an inch in diameter and to a depth of four inches or so into a wooden block, and placing the block in a sheltered situation well off the ground, you can provide housing for these beneficial bugs.

The nest tunnel is divided into cells with partitions usually made of plant or tree resin. Each cell is provisioned with a number of paralyzed or dead aphids (from six to over sixty according to the literature) and an egg laid on one of those victims. The female wasp may sting an aphid victim, or crush it to death in her jaws, before taking it back to the nest.

Nests of Passaloecus ithacae may contain six to twelve cells each (Krombein, 1967). There are two generations annually, at least in Erie County, New York. Nests of this and other species of Passaloecus are subject to parasitism from the cuckoo wasp Omalus aeneus and the ichneumon wasps Poemenia albipes and P. americana.

We tend to think of lady beetles and lacewings as the prime predators impacting aphid populations, but Passaloecus and related genera of wasps clearly have an effect as well. Perhaps we need to re-think our assumptions and expand our natural allies in pest control to include wasps (Corbet & Backhouse, 1975).

Sources: Bohart, R. M. and A. S. Menke. 1976. Sphecid Wasps of the World. Berkeley: University of California Press. 695 pp.
Corbet, Sarah A. and M. Backhouse. 1975. “Aphid-hunting wasps: a field study of Passaloecus,” Trans R Entomol Soc Lond 127(1): 11-30.
Fricke, J. M. 1993. “Aphid prey of Passaloecus cuspidatus (Hymenoptera: Sphecidae),” Gt Lakes Entomol 26(1): 31-34.
Krombein, Karl V. 1967. Trap-Nesting Wasps and Bees: Life Histories, Nests and Associates. Washington, DC: Smithsonian Press. 496 pp.
http://researcharchive.calacademy.org/research/entomology/Entomology_Resources/Hymenoptera/sphecidae/Genera_and_species_pdf/Passaloecus.pdf

Spider Sunday: Mystery Solved

2011-11-07T08:54:00.000-08:00

Note: This post originally appeared on Sunday, November 6, but I pulled it in the wake of what turned out to be mostly a misunderstanding. After careful deliberation I am resurrecting the story. I think it is instructional in terms of how problems like this are resolved. I normally do not charge a fee for a simple identification, but this was an exceptional case involving a corporation with much to lose without intervention.

This past Wednesday, November 2, I was presented with a unique opportunity to solve an arthropod mystery for a corporate client. A friend in state government sent me a message on Facebook that morning asking myself and another colleague who we would recommend for identifying spider specimens for a company in an Atlantic coast state. I wrote back that the inquiring party could send specimens to me, but that I would charge a modest fee for my expertise. My government friend thought that seemed reasonable and put me in touch with the company representative.

Later that morning I received a phone call from the Director of Regulatory Compliance for the company suffering from a “spider infestation” in a recent shipment of merchandise from overseas. He decided he would overnight specimens to me for examination.

The next morning, the company rep e-mailed me with two images of the spiders in question. I was pleasantly surprised by the detail in those pictures:

It was clear to me from the images that the spiders were some kind of “cellar spider” in the family Pholcidae, but I could not conclude what genus, let alone species, without putting actual specimens under a microscope. At least I could tell him that the arachnids were nothing considered to be dangerously venomous according to current scientific understanding. Time was of the essence and I hoped that my reply to his e-mail might be sufficient.

I received a message from FedEx with a tracking number for the package, and discovered that I would not receive the shipment until Friday morning. Meanwhile, I did not hear back from my company contact.

Indeed, I heard a knock on my door around 10:00 AM on October 4, and there was the FedEx delivery person with a box for me. Interestingly, he seemed quite eager to part with the parcel….

I was amused to find that inside this rather large box was a great quantity of bubble-wrap and a teeny-tiny little vial with a single spider inside. I believe the spider was actually alive when it was packed up, though it was deceased when it arrived. It was still limber and in no way compromised in its anatomical integrity.

I gently placed the creature into a glass petri dish and under my microscope. It was immediately apparent that I had an immature specimen, which would make identification more difficult than it would be with an adult specimen. Still, I broke out my “bible,” the Spiders of North America: an identification manual, turning to the family Pholcidae. The key to genera was sufficient enough for me to conclude that the spider belonged to the genus Pholcus: eight eyes, not six; no pit or groove in the carapace.

Up until recently, it would have been safe to extrapolate to the species P. phalangioides, the “Long-bodied Cellar Spider,” a very abundant and widespread species. However, I learned from my arachnologist colleague that another species of Pholcus, P. manueli, is expanding its range in the United States. Further, there are evidently a number of undescribed species in the genus.

I called the company representative today with the verified identification.

Wasp Wednesday: Pollen Wasp

2011-11-02T13:23:00.000-07:00

Today, as I write this, there is snow on the ground and the temperature is somewhere in the 20s (Fahrenheit). You can’t blame me for harkening back to July 11 when it was warm and I was hiking with friends in Emerald Valley near Cheyenne Mountain here in the Front Range of Colorado. One of the insects that excited me the most that day was Pseudomasaris vespoides, one of the “pollen wasps” that stands in such stark contrast to its social and predatory relatives.

Pollen wasps comprise the subfamily Masarinae in the family Vespidae. They collectively occur across the globe, in western North America, southwestern South America, northern and southern Africa, southern Europe, central Asia, and most of Australia, absent from tropical regions. Only the genus Pseudomasaris exists in North America, with 14 species.

These are solitary wasps, each female constructing her own mud nest and provisioning each cell with pollen and nectar, more like a bee than a wasp. The wasps visit Penstemon, or Phacelia and Eriodyction almost exclusively, with additional records for some other flora genera. This pollination relationship is termed “oligolectic” when an insect is obliged to harvest pollen from such a limited diversity of flowers.

The female Pseudomasaris vespoides that I observed on that July day were all visiting Penstemon blossoms. I did not see any males, but populations of this wasp peak in late June with males emerging before females, so their absence later in the year would not be peculiar. Males, easily identified by their very long, clubbed antennae, patrol patches of flowers likely to be visited by females. This is in contrast to the hilltopping behavior of P. maculifrons that I addressed in a previous post.

Females fashion earthen nests comprised of several cells. While most Pseudomasaris adhere their nests beneath stones or other sheltered situations, P. vespoides tends to attach its nests to twigs out in the open, like the one shown below, from Catalina State Park in southern Arizona. The nests may be parasitized by the cuckoo wasp Chrysurissa densa.

P. vespoides is a relatively widespread species, occurring from Washington state south to California, Arizona, and New Mexico, east to Wyoming, Nebraska, and South Dakota. Females and males are about the size of your average yellowjacket wasp and can easily be mistaken for their social cousins. Pollen wasps, however, do not have the longitudinal fold that other vespid wasps display when the insects are at rest. Pollen wasps also have clubbed antennae, whereas other vespids do not.

Sources: Gess, Sarah K. 1996. The Pollen Wasps: Ecology and Natural History of the Masarinae. Cambridge, Massachusetts: Harvard University Press. 340 pp.
Richards, O. W. 1963. “The Species of Pseudomasaris Ashmead (Hymenoptera, Masaridae). University of California Publications in Entomology 27(4): 283-310.

Spider Sunday: Cat-faced Spider

2011-10-30T06:00:00.000-07:00

Here in the western United States, one of the most common orb weavers is the Cat-faced Spider, Araneus gemmoides. I do not find them to be that conspicuous, however, because the spiders hide in their retreats by day, emerging only at night to sit in the hub of their spiral snares.

This species is known in parts of Canada as the “Jewel Spider,” but its more common name of “Cat-faced Spider” is more descriptive. Araneus gemmoides is one of the angulate orb weavers that often sport a pair of conical humps near the front of the top of the abdomen. These “horns” mark the “ears” of the cat face, with variable markings on the abdomen reinforcing the feline moniker.

One variation, the “Cheshire Cat-faced Spider,” has only a smiley-face….Ok, I’m making things up now, but the pattern of markings is highly variable in this species. One reasonably consistent mark is a short, white vertical stripe on the front edge of the abdomen, usually crossed by two white chevrons.

Mature females are large spiders, especially when gravid, their abdomen full of eggs. They vary in body length from 13-25 mm. Males, in contrast, are a mere 5-8 mm as adults.

Cat-faced Spiders spin rather small webs in proportion to their body size, the prey-catching zone spanning maybe one foot or so, even if the foundation lines of the snare may stretch several feet between anchor points. The occupant invariably sequesters herself in a curled leaf or other retreat by day, sometimes still monitoring the web via a signal line running from her retreat to the hub.

As darkness falls, the spider emerges to repair its web, or simply spin a new one, after which she may settle in the center of the web, head down, to await potential prey.

In optimal situations, several individual spiders may spin their webs in close proximity. My friend Margarethe Brummermann showed me a small group of these spiders that occupied a cliff face in Peppersauce Canyon on the north side of the Santa Catalina Mountains in southern Arizona. Much attention is paid to the fact that A. gemmoides will spin its webs on or about homes and other buildings, but they are likely taking advantage of outdoor lighting that attracts large numbers of insects within range of their webs.

Females apparently spin only one egg sac in late autumn. The spiderlings emerge the following spring and disperse. Young spiders have exaggerated humps on their abdomen, like the one shown below. Perhaps they have to “grow into them.”

The Cat-faced Spider ranges from British Columbia and Saskatchewan east to Michigan and south through the Dakotas, Rocky Mountains, and Pacific states to Arizona. Look for mature individuals in late summer and throughout the fall.

It's 'Hopper Time!

2011-10-28T13:42:00.000-07:00

Among the last insects to be seen or heard before the hard frosts of late autumn are grasshoppers. Diversity of the short-horned grasshoppers in the family Acrididae is especially great in the desert southwest and the Great Plains. Here in central Colorado, we have plenty of representatives from both of those areas, convening here on the Front Range.

I have only been here since October third, and I’ve already tallied 25 species, thanks to help from David J. Ferguson via Bugguide.net. Here is the list:

White-whiskered Grasshopper, Ageneotettix deorum

Western Spotted-wing Grasshopper, Cordillacris occipitalis

Velvet-striped Grasshopper, Eritettix simplex

Two-striped Mermiria, Mermiria bivittata

Wyoming Toothpick Grasshopper, Paropomala wyomingensis

Brown-spotted Range Grasshopper, Psoloessa delicatula

Speckle-winged Rangeland Grasshopper, Arphia conspersa

Northwestern Red-winged Grasshopper, Arphia pseudonietana

Clear-winged Grasshopper, Camnula pellucida

Northern Green-striped Grasshopper, Chortophaga viridifasciata

Wrangler Grasshopper, Circotettix rabula

Hayden’s Grasshopper, Derotmema haydeni

Carolina Grasshopper, Dissosteira carolina

Dusky Grasshopper, Encoptolophus costalis

Platt Range Grasshopper, Mestobregma plattei

Mottled Sand Grasshopper, Spharagemon collare

Finned Grasshopper, Trachyrhachys aspera

Kiowa Rangeland Grasshopper, Trachyrhachys kiowa

Pallid-winged Grasshopper, Trimerotropis pallidipennis

Red-shanked Grasshopper, Xanthippus corallipes

Two-striped Grasshopper, Melanoplus bivittatus (top of post)

Differential Grasshopper, Melanoplus differentialis

Gladston’s Spurthroated Grasshopper, Melanoplus gladstoni (above)

Lakin’s Grasshopper, Melanoplus lakinus

Migratory Grasshopper, Melanoplus sanguinipes

Most of the above were found as adults, sometimes with tattered wings or an absent leg or two. Some are nymphs at this time of year that will overwinter and become adults next spring. These includes the Velvet-striped Grasshopper, Brown-spotted Range Grasshopper, Speckle-winged Rangeland Grasshopper, Northern Green-striped Grasshopper (below), and Red-shanked Grasshopper.

Here in Colorado Springs, I’ve encountered 20 species. Different habitats, elevations, and micro-climates have their own unique fauna. The Two-striped Mermiria (below), for example, was found along the Arkansas River in Cañon City. These large slant-faced grasshoppers are more fond of riparian corridors with tall, thick grass.

Hayden’s Grasshopper and the Wyoming Toothpick Grasshopper were both seen in very short grass at Fountain Creek Regional Park, in a field just in front of the nature center.

At higher elevations, one can find the Wrangler Grasshopper, Circotettix rabula. These insects can sustain their noisy flights for many seconds, in contrast to most other grasshoppers. They frequent steep slopes with scree (broken rock fragments), however, so it is a dangerous challenge to get images of them. The image below came from Emerald Valley back in July, when I could shoot from a trail above the insect.

The cooler temperatures of autumn mean that grasshoppers struggle to keep warm. Many of them adopt "basking" postures like the Carolina grasshopper pictured below. The insect literally leans back to expose one side of its body fully to the sun. It even lowers its hind leg so as not to block heat from reaching its abdomen.

You can find images of most of the above species in my “grasshoppers” set on Flickr.com. I’m already looking forward to next spring, when some of the nymphs will be large, colorful adult insects. I’ll bring you the results then, too.

Wasp Wednesday: Western Paper Wasp

2011-10-26T06:00:00.000-07:00

Here in central Colorado we are experiencing higher-than-normal autumn temperatures. Several record highs were broken Monday, October 24, 2011 in fact. The warmth has meant that most of the social wasps are still active. Among the most common of those is the Western Paper Wasp, Mischocyttarus flavitarsis. This insect can easily be mistaken for a species of Polistes, but Mischocyttarus has a petiolate (stalked) abdomen in contrast to the more sessile abdomen of Polistes.

Mischocyttarus is a genus of roughly 260 species that is most diverse in the neotropics of Central and South America. Their classification has presented something of a nightmare to entomologists and it seems the end is nowhere in sight. Currently, there are three recognized species that make into the United States and southwest Canada, all in the subgenus Phi. Here in the western U.S., only M. flavitarsis occurs, but it ranges from British Columbia to Mexico, east to Nebraska and west Texas. I have encountered the subspecies M. f. navajo in Arizona (see image below), which is also found in Mexico.

This genus constructs small, uncovered paper combs essentially identical to the nests of Polistes paper wasps. My personal observations of M. flavitarsis flavitarsis in Portland, Oregon have demonstrated that the wasps prefer to nest in cavities. This may be in response to the rainy climate there, and/or offer greater protection from birds. Avian predation is a chief mortality factor for larvae and pupae of other species in the genus (Hermann & Chao, 1984). Certainly, nests I have found elsewhere have been more exposed, such as the M. mexicanus mexicanus nest imaged below at Resaca de la Palma State Park near Brownsville, Texas.

Like other paper wasps, Mischocyttarus females prey primarily on caterpillars to take back to the nest and feed their larval siblings. A study of M. flavitarsis demonstrated that the wasps rely mostly on olfactory cues for detecting prey. They may home in on volatile chemicals secreted by plants in the wake of damage from caterpillars, and especially the odor of the droppings or “frass” left behind by feeding caterpillars (McPheron & Mills, 2007).

The adult wasps themselves frequently seek out colonies of aphids to sip the sugary “honeydew” secreted as a waste product by the aphids. You may find an abundance of wasps, flies, and other insects around deciduous trees, and even pine trees that are infested with aphids.

Male behavior is geared to finding mates. A study of M. flavitarsis navajo in Arizona revealed that in late summer, males “patrol” areas frequented by females. Riparian corridors are a typical location for this activity. Each male will stop frequently to scent-mark twigs, foliage, and other objects with a chemical secreted by his abdomen. The male vigorously defends his marked patches from competing males.

Males that emerge in the fall form leks near potential hibernation sites. A lek is a stage where males congregate to show off to females. In this instance, each male simply scent-marks a perimeter roughly ten centimeters in diameter and sticks to this territory. Incoming females are free to choose (or reject) any male without interference from other males.

At this time of year, females of Mischocyttarus are seeking places to hibernate. Males may seek shelter as well, but they are unlikely to survive until the following spring. The females may spend the colder months under rocks, logs, under loose bark on trees, in the attics of homes, or other protected niches. They can congregate peacefully with others of their kind, and even with Polistes paper wasps. Warm winter days may find the wasps emerging to bask and explore their immediate surroundings.

Mischocyttarus is one of many social wasps that can be observed even at fairly close range without interfering with their behavior or eliciting an attack response. Take time to get to know them. You might learn something that nobody else has yet seen.

Sources: Hermann, Henry R. and Jung-Tai Chao. 1984. “Nesting biology and defensive behavior of Mischocyttarus (Monocyttarus) mexicanus cubicula (Vespidae, Polistinae),” Psyche 91: 51-66.
McPheron, Linda J. and Nick J. Mills. 2007. “Influence of visual and olfactory cues on the foraging behavior of the paper wasp Mischocyttarus flavitarsis (Hymenoptera: Vespidae),” Entomol Gener 30(2): 105-118.
Preston-Mafham, Rod and Ken. 1993. The Encyclopedia of Land Invertebrate Behavior. Cambridge, Massachusetts: The MIT Press. 320 pp.
Silveira, Orlando Tobias. 2008. “Phylogeny of wasps of the genus Mischocyttarus de Saussure (Hymenoptera, Vespidae, Polistinae),” Rev. Bras. Entomol. 52(4).

Spider Sunday: Banded Argiope

2011-10-23T06:00:00.000-07:00

In my three weeks as a new resident of Colorado Springs, I haven’t seen that many spiders, let alone orb weavers. I look up for the webs, but sometimes forget to look down. Some of our most spectacular orb weavers, in the genus Argiope, usually build their spiral snares close to the ground amid tangled weeds and other vegetation. It was by chance and the angle of sunlight that I spotted the webs of two Banded Argiope spiders, Argiope trifasciata, yesterday.

This spider is common over the entire United States, and warmer regions of the globe, though it is reportedly rare in southern Europe. Here in North America, adult specimens can be found deep into autumn. According to a fact sheet on this species from Penn State University, A. trifasciata has a strategy for enduring the cooler fall temperatures: The spiders orient their webs east to west, with the animal itself hanging head down in the center of the web. The ventral surface of the spider’s body, largely black in color (see the image below),

faces south, catching the sun’s warming rays. Studies also indicate that these orb weavers could easily overheat during the late summer (Tolbert, 1979; Ramirez, et al, 2003), so the webs are then oriented to reduce the spider’s exposure to full sun. The spiders even “obelisk” to a degree, tilting their abdomen away from the web surface to minimize or maximize exposure to the sun. The dorsal surface of this species is highly reflective, mostly silver in color with darker bands across the abdomen. Specimens vary considerably in the degree of banding, and just how dark those bands can be. Additionally, an inverted trident pattern is often visible on the top of the abdomen, the “tines” directed toward the rear of the arachnid.

The females are large arachnids, mature specimens ranging in body length from 15-25 millimeters. Males, on the other hand, are petite, only 4-5.5 millimeters.

This species often occurs in habitats frequented by its cousin, the Black and Yellow Argiope, A. aurantia. The two spiders do look essentially identical on the underside, but note that the legs of the Banded Argiope are annulated, whereas the extremities of the Black and Yellow Argiope are reddish brown basally and mostly black distally. The abdomen of the Banded Argiope is also quite pointed in contrast to the more broadly oval, blunt-ended abdomen of the Black and Yellow Argiope.

Females fashion an egg sac shaped like a kettledrum, flat on the upper surface and highly convex otherwise. The tough, papery silk on the exterior of the egg sac helps camouflage the package amid the dry, dead autumn weeds.

I find this spider to be strikingly beautiful. I can still recall the first one I saw as a child in Portland, Oregon. She had her web amid an ornamental, low-growing juniper along the steps to our front door. I could visit her every day once I knew where to look. My friend and mentor, naturalist Jim Anderson, was the one who helped me identify her as I remember.

Such can be the positive power of nature’s cryptic beauty if you are not prone to arachnophobia. There is really no substitute for getting out from behind the computer screen, television, or even the book or magazine and going exploring outside your home. Your very backyard can hold amazing surprises to rival the most exotic creatures of the Amazon.

Sources: Hillyard, Paul. 1997. Collins Gem Spiders Photoguide. Glasgow: Harper Collins Publishers. 254 pp.
Kaston, B. J. 1978. How to Know the Spiders (Third Edition). Dubuque, Iowa: Wm. C. Brown Company. 272 pp.
Ramirez, Martin G., Estelle A. Wall, and Monica Medina. 2003. “Web orientation of the banded garden spider Argiope trifasciata (Araneae, Araneidae) in a California coastal population,” The Journal of Arachnology 31: 405-411.
Tolbert, Wayne W. 1979. “Thermal stress of the orb-weaving spider Argiope trifasciata,” Oikos 32(3): 386-392.

Wasp Wednesday: Western Yellowjacket

2011-10-19T09:54:00.000-07:00

Notorious. That describes the Western Yellowjacket, Vespula pensylvanica (and yes, the species name is spelled correctly). I recall this social wasp from my childhood in Portland, Oregon where it was a constant presence at picnics, barbecues, and garbage cans at the zoo and every other urban park. Here in Colorado Springs they are equally pestiferous, and persist deep into the fall.

Each year, the Western Yellowjacket colony cycle begins with queens searching for nesting sites. These females are larger, and more yellow in color than the worker caste. They typically emerge from their winter hibernacula sometime between March and April, though it may take awhile for a queen to find a suitable subterranean niche where she can start building her nest. I imaged the queen below at the Cheyenne Mountain Zoo on July 9, 2011, so she still had no help from workers in constructing her nest.

Once the queen’s worker offspring can contribute, the colony and nest quickly expand in size. Mature nests, based on records from Pullman, Washington and La Grande, Oregon, can exceed a population of 2,000 workers (average about 1,800) and contain 4,000 cells or more in the paper combs.

Nests are usually located in abandoned rodent burrows ten to fifteen centimeters below the surface of the soil, with entrance tunnels ten to thirty centimeters long. There is often a mud turret surrounding the entrance hole. Look for yellowjackets coming and going from the same spot to locate a nest entrance. You can approach closely to watch their activity without arousing the occupants, but run a lawnmower over the nest and watch out! One of my elementary school science teachers told me he once drove a stake right through a nest. That could not have been a pleasant experience.

Western Yellowjackets are best known for their aggressive scavenging behavior. They have to secure large quantities of protein to feed the larvae in the nest, and the workers take that job seriously. It is much easier to haul away a chunk of your tuna sandwich, chicken leg, or burger than it is to go kill a series of small insects. Still, this species does its fair share of scavenging road kill and preying on true bugs, spiders, flies, grasshoppers, even slugs.

The adult wasps need carbohydrates to fuel their active lifestyle, so that is why they crawl into your soda can. Normally, in nature, they prefer the sweet waste products secreted by aphids and scale insects. This “honeydew” is like the Nectar of the Gods to social wasps. Last week I imaged several workers lapping up the honeydew of Cinara conifer aphids on a pine tree at the Cheyenne Mountain Zoo.

The last chapter in the annual colony life cycle is the production of new queens and males. These reproductives are liberated at the end of the season and they fly out to find mates from other colonies. The males, with their long abdomens and antennae, seem to congregate around the tops of small trees where they perch to await passing females. The males may dislodge each other from prime lookout posts, but they don’t have stingers and such squabbles are therefore not life-threatening.

Western Yellowjackets can be “bad” some years, with much higher than normal population densities. This usually occurs when a warm, dry spring season allows queens to get a head start on establishing colonies. The result can be worker wasps wreaking havoc on fruit tree orchards, logging camps, and outdoor recreation destinations later in the summer.

The Western Yellowjacket is exactly that: a western North American species ranging from southern British Columbia, Alberta and Saskatchewan south through the Pacific coast and Rocky Mountain States, all the way to Arizona and New Mexico at higher elevations. There are scattered records across the northern Midwest as far east as Michigan; and this species has been introduced to Hawaii as well.

Source:Akre, Roger D., Albert Greene, et al. 1981. The Yellowjackets of America North of Mexico. Washington, DC: USDA Agriculture Handbook Number 552. 102 pp.

Spider Sunday: Triangle Spiders

2011-10-16T06:00:00.000-07:00

The following is a “reprint” of a blog entry for September 10, 2009.

An outing to the Westfield River in Hampshire County, Massachusetts last Sunday, September 6, included a stop at the Knightville Dam, where a unique arachnid awaited my discovery. There, among the goldenrods, asters, and ornamental black locust trees I found two triangle spiders, named for the shape of their web: a triangle that is essentially the sector of an orb web. The reduced size of the snare is just one puzzling feature of these amazing spiders.

Triangle spiders belong to the genus Hyptiotes (pronounced Hip-tee-OH-teez) in the obscure family Uloboridae. They are part of a larger group of arachnids called “cribellate spiders.” Cribellate spiders all share one feature in common: an extra spinning organ called a cribellum, located adjacent to the normal group of spinnerets. The cribellum issues a special type of silk that the spider literally “fluffs up” using a comb-like organ called a calamistrum, located on each hind leg.

Perhaps even more amazing than the “accessories” that uloborids have is what they lack. These are the only spiders in North America that do not have venom glands. That’s right, they are non-venomous spiders. So, you ask, how then do they subdue their prey? That is a great question for which I have not the foggiest answer. They probably do an extra-good job of wrapping their prey in silk, but not just any silk.

The cribellate silk threads in the part of the web designed to trap insects is not sticky like you would expect. Instead, it is tangled, and this is apparently just as effective as little droplets of glue.

Once it has erected its snare, the triangle spider sits on the thread near the tip of the twig or grass stem to which the apex of the triangle is secured. Depending on which book or article you believe, the spider either bridges a gap in this anchor thread, or simply perches there and reels in the slack line to render it taut. When a prey insect impacts the web, the spider then instantly releases the anchor thread, causing the web to rebound, further entangling the prey.

This feat of engineering and strength is performed by a very small animal. Even an adult female Hyptiotes is only 3-4 millimeters long. Males are 2-3 millimeters at maturity. Simply spotting one of these spiders is cause for self-congratulations for any naturalist.

There are four species of Hyptiotes in North America, three of which are chiefly western in their geographic distribution. The one shown in the image here is Hyptiotes cavatus, the sole eastern species.

Keep a sharp eye out for triangle spiders. The webs are mostly built about waist-high in weeds, on bridges and other structures, and twigs of trees and shrubs.

Wasp Wednesday: Prairie Yellowjacket

2011-10-12T14:46:00.000-07:00

Arriving in Colorado Springs in early October, I was not optimistic that I would find many, if any, wasps still active in the chilling air. Much to my surprise there are still some on the wing, even at high altitudes. Monday, October 10, Heidi and I traveled up into the Front Range to Cripple Creek and the surrounding area. There, walking around on the snow, I found a male Prairie Yellowjacket, Vespula atropilosa.

Heidi remarked that she thought the Western Yellowjacket, Vespula pensylvanica was the only species of that genus living in the area. Actually, there are six species total known from Colorado. Yellowjackets could be considered mostly boreal in their distribution patterns, ranging south at higher elevations where the climate resembles that of higher latitudes.

This particular specimen could have been blown up to its 9,000 foot or so location, too. The colonies of V. atropilosa tend to be smaller than those of more “urban” species, and usually decline earlier in the season, too, so I was somewhat surprised to see this one.

This male exemplifies the yellow or “xanthic” phase of this species. They also come in a black or “melanic” phase that is more black than yellow, as shown in the diagram below from Roger D. Akre’s The Yellowjackets of America North of Mexico (USDA Agriculture Handbook No. 552, 1981), and another specimen I imaged on October 13 in Colorado Springs.

The Prairie Yellowjacket nests preferentially in abandoned rodent burrows. Nests have also been discovered in tree hollows, under steps, and between the walls of houses. One truly aerial nest was found in Pullman, Washington, but this is decidedly an anomaly. The paper combs are surrounded by layers of “envelope,” typically rather coarse as is the case in most subterranean yellowjacket species. V. atropilosa nests are dirtier than most, with the bodies of deceased wasps and other debris incorporated into the paper envelope.

The greatest number of workers in any of the nests studied by Dr. Akre and his colleagues was 504. These are not your picnic-harassing, garbage-gathering yellowjackets, either. They have retained their predatory nature and hunt mostly spiders, harvestmen, flies, insect larvae, and true bugs as food for the larvae back in the nest. Adults feed on aphid honeydew and flower nectar to fuel their flight.

The Prairie Yellowjacket is restricted to western North America, ranging from central British Columbia south and east through southern Alberta, Washington, Oregon, California, Idaho, western Montana, Wyoming, Utah, most of Colorado, and northern New Mexico and Arizona. It avoids nesting in truly urban locations in my experience, though nests in yards are apparently not uncommon.

I look forward to finding more interesting yellowjacket species here in the Rocky Mountains, and I reserve the right to revisit this particular species in future blog posts.

Spider Sunday: Arachtober, 2011

2011-10-09T07:00:00.000-07:00

It seems like only yesterday that I announced the annual Flickr photo group ”Arachtober” at my other blog, Sense of Misplaced. Well, it is that time of year again, and this year’s edition of the online event is poised to be the best ever.

One needs to have a Flickr account to join the Arachtober group. Then, you must be approved by the group administrator, though this is usually only a formality. Right now, group members can only post one image of a spider, scorpion, or other arachnid per day. Later in the month the limit will increase. The images you contribute should not be ones posted to your Flickr page in previous months.

The fact that Arachtober falls in the same month as Halloween is no coincidence, but the goal of Arachtober is to celebrate the diversity, beauty, and positive impact of our arachnid friends. It is a perfect antidote to haunted house cobwebs and scary fake spider decorations.

Once again I encourage all my arthropod-loving photographer friends to share their favorite images with an audience of other arachnophiles. Please see the above link to my original post for more information on the origin of the event. Thank you.

We're Moving!

2011-09-25T11:20:00.000-07:00

Well, the blog is staying put, actually, but the author is moving from Tucson, Arizona to Colorado Springs, Colorado next weekend. This blog will be on hiatus until he gets settled and hooked up with whatever internet provider serves his neighborhood there. Thank you in advance for your loyalty and patience. I am optimistic that I'll be back by mid-October.

Wasp Wednesday: Triscolia ardens

2011-09-21T12:02:00.000-07:00

Have you ever been involved in a hit-and-run accident? If so, then you know what it feels like to be a scarab beetle grub being attacked by a scoliid wasp. The only difference is that the insect encounter is no accident. Female scoliid wasps actively seek out the beetle grubs as hosts for their larval offspring. Here in southern Arizona, one of the largest and most conspicuous of the scoliids is Triscolia ardens.

T. ardens is the only member of its genus in North America north of Mexico. It occurs from Texas to southern California and is relatively common. Females are robust, with short antennae. Males have long antennae and sport a three-pronged "pseudosting" at the tip of the abdomen. The remainder of this post will treat scoliids in general because so little is known about the biology of individual species.

Scoliids of both genders can be found visiting flowers, especially milkweed, seep willow (Baccharis), saltcedar (Tamarix), desert willow (Chilopsis), mesquite (Prosopis), scalebroom (Lepidospartum), and buckwheat (Eriogonum). At the end of the day, the wasps bed down singly on vegetation, remaining alert but not not terribly motivated to move as the desert temperatures begin to fall.

Their life cycle can be generalized as follows. The female wasps fly low over the ground, somehow divining the presence of subterranean scarab beetle grubs. Once one is detected, the wasp digs it up, using her densely spiny legs to send the soil flying. Once she unearths the grub, she stings it into paralysis. This allows her to lay a single egg on the grub. After she accomplishes her mission, she re-buries the grub and flees the scene of the crime (some species have been observed moving the grub deeper into the soil and fashioning an earthen cell around it before depositing an egg and sealing the tunnel). The beetle grub apparently never recovers from its coma. The egg of the wasp hatches, and the larva that emerges will feed as an external parasite on its host for about a week or two before spinning a silken cocoon and pupating. Most North American scoliids overwinter in the pupal stage.

The size of the mature wasp is dependent on the size of the host beetle grub. Even the largest Triscolia ardens seldom exceed about 30 millimeters in body length, but one frequently finds “dwarfs” that obviously suffered a lack of nutrition in their youth. Tropical scoliids, however, are among the largest (certainly heaviest) wasps in the world, exceeding 50 millimeters in body length.

Other online resources include this PDF on scoliid wasps of Florida. It is an excellent introduction to the family as a whole, treating Florida scoliids in particular. Another PDF on Scoliidae of California addresses some southwestern species but it appears incomplete.

Clearly, much remains to be learned about these highly attractive and obvious wasps. Any documentation with video is likely to be a first, or nearly so; and host associations are almost entirely lacking for our native scoliids (some species have been introduced to the U.S. to control exotic scarab pests).

Spider Sunday: Pirate Spiders

2011-09-18T13:26:00.000-07:00

Arrrr, matey! In honor of International Talk Like a Pirate Day (tomorrow, September 19), I bring ye the story of pirate spiders in the family Mimetidae. I’m not pulling your beard, there really are such creatures.

The mimetids are represented by a total of three genera and eighteen species in North America north of Mexico, though another ten remain undescribed (awaiting the assignment of names by arachnologists).

Pirate spiders are easily identified by their four eye patches and two wooden legs. But seriously, folks, the long spines on their legs help differentiate them from the cobweb spiders and sheet-web weavers that they might otherwise be mistaken for. Their resemblance to other spiders is further complicated by the fact that you sometimes find pirate spiders in the snares of cobweb weavers. Their appearance there is as sinister as their name suggests.

Pirate spiders eat cobweb spiders, as well as orb weavers and other spiders. They stealthily stalk the rightful owner of the web, finally dispatching it by biting the other spider on its legs. The pirate spider feeds on one leg after the other until its victim is totally drained. One reason for attacking the legs of its prey might be that the jaws of pirate spiders are fused at their base, not permitting the spider to open its mouthparts wide enough to bite other parts of its victims.

Pirate spiders can also feed on insects when presented with the opportunity, but their venom is designed to kill other spiders quickly. They will also eat the egg sacs of their victims. This lifestyle has given rise to another popular name for them: “cannibal spiders.”

The specimen imaged above is Mimetus puritanus, the most common species in the eastern United States. I found this one in South Deerfield, Massachusetts on October 21, 2009. The male specimen below (note the modified pedipalps) was discovered on the ceiling of my residence on July 23, 2009. At only 3-7 millimeters in body length, pirate spiders in general are not terribly imposing for creatures that make their living attacking other spiders.

My girlfriend found the egg sac of a Mimetus in Colorado Springs, Colorado on July 28 of last year. The “fluffy” appearance of the sac’s loosely-woven silk is fairly diagnostic for the genus.

I encountered what appears to be a different species of Mimetus at Bentsen Rio Grande Valley State Park in Mission, Texas on June 7, 2010. It was occupying the web of a theridiid cobweb weaver, and until I cropped my images, that is exactly what I thought it was.

Well, my swashbuckling friends, keep yer eyes peeled fer them thar buccaneer arachnids we call pirate spiders. Arrr!

Wasp Wednesday: Polistes arizonensis

2011-09-14T18:53:00.000-07:00

Here in southern Arizona there are several species of paper wasps in the genus Polistes. What intrigues me is that you seldom find more than one species in any particular location. At the least, one species is usually dominant and other species scarce. Here in the city of Tucson, one of the more abundant urban species is P. arizonensis.

At first glance, this species could be mistaken for Polistes exclamans, a species common in the eastern and southern U.S. Indeed, P. arizonensis was once considered a subspecies of P. exclamans. The Arizona wasp only ranges from Arizona to southern California and Mexico.

One of the favorite places for P. arizonensis to nest is under collapsed palm fronds. Several large colonies can coexist in close proximity under these weathered but sturdy leaves. Here is an example I found at the Sweetwater Wetlands in northwest Tucson.

I have found several female (worker) wasps overwintering on such insulated nests, so the large combs may represent the expansions of the previous year’s occupants. Well, that was my theory until I took some of these old nests as souvenirs and found they harbored huge numbers of dermestid beetle larvae that eventually became adult beetles flying freely around my apartment. The invasion of scavengers like dermestids suggests that the combs held deceased wasps (probably in the pupal stage), and those cells are not likely to be re-used.

Interestingly, Polistes arizonensis seems just as comfortable nesting amid tangled shrubbery, which leaves them perhaps more exposed to the elements, and their prime enemies: ants. The wasps do have an answer for the ants, though. The female wasps secrete a substance that repels ants, and apply this blackish goo liberally to the paper pedicel that attaches the nest to the substrate (stem, frond, ceiling, whatever). The repellant is produced by sternal glands located internally on the underside of the abdomen. The secretion consists of long-chain carboxylic acids. One study showed that the unsaturated acids (palmitoleic, linoleic, and oleic) in the secretion were effective in repelling at least three species of ants, for up to four days (Dani, et al., 1996).

Like most paper wasps, P. arizonensis seems to prefer hunting caterpillars as food for the larvae back at the nest. Notice the worker chewing up a caterpillar in the image below, prior to feeding the morsel to a larva in one of the cells in the nest.

This nest was located under the sheltering roof of a “ramada” overlooking one of the ponds at Sweetwater Wetlands.

You can tell the gender of many kinds of paper wasps by looking them in the face. Females usually have dark, triangular faces, whereas males have square, yellow faces. Such is the case with P. arizonensis. Also note the hooked tips on the antennae, and blunt tip of the abdomen in the male specimen imaged below.

I find that this species is remarkably tolerant of close approaches to its nests. I was able to get these images without the occupants even taking an alarm stance. When paper wasps stand on tip-toe (tip-tarsi?), with wings raised and splayed, it means “You have come too close! Back off now or suffer the consequences.” By retreating even a short distance after such a warning you prevent an attack and the wasps go back to business as usual. Understand that I am not recommending you trespass active colonies, but do use your own judgment and enjoy observing their interactions.

Sources: Dani, F. R., S. Cannoni, S. Turillazzi, and E. D. Morgan. 1996. “Ant repellent effect of the sterna gland secretion of Polistes dominulus (Christ) and P. sulcifer (Zimmermann). (Hymenoptera: Vespidae),” Jour. Chem. Ecol. 22: 37-48.

Spider Sunday: Dewdrop Spiders

2011-09-11T15:25:00.000-07:00

Last week I wrote about one of North America’s largest spiders, the Golden Orb Weaver (Argiope aurantia). While photographing the specimen from Ohio last month (see below), I discovered something amazing: a dewdrop spider was living on the web of the orb weaver.

It turns out that this itty-bitty spider (below) lives as a “kleptoparasite” of the orb weaver.

Kleptoparasites are animals that steal the food of their hosts. Indeed, that is what a dewdrop spider does. Whether or not its activities impact the host spider is debatable. A study of a species that lives in the webs of Nephila orb weavers revealed that host spiders do not gain weight as much as spiders that do not host dewdrop spiders, and that they relocate their webs more often than non-host specimens (Grostal and Walter, 1997).

Dewdrop spiders are in the cobweb weaver family Theridiidae, and genus Argyrodes.
There are three species in North America, all confined to the United States, and mostly the southern U.S. The species imaged here might be Argyrodes elevatus. Interestingly, in this genus the males are usually larger than the females. The modified pedipalps of “my” specimen reveal it to be a male.

Some Argyrodes have been recorded as actually preying on the host spider. I found a paper online that documented this for a species that uses labyrinth spiders (Metepeira sp.) as a host (Wise, 1982). That makes sense. Argyrodes are tiny, only 2-4 mm in body length, and I can’t see them killing something as large as a female Argiope or Nephila. Maybe they can kill intruding males, though. Given that male Argiope and Nephila are several orders of magnitude smaller than females, they could indeed be vulnerable to an ambitious Argyrodes. Both kinds of spiders tend to frequent the perimeter of an orb web, too, where they would easily come into conflict.

Argyrodes may be considered as being “commensal” when it only takes prey in the host web that is too small for the host to bother with (like the tiny winged ant in the images here). Commensalism is defined as a relationship whereby one organism benefits and the other is not affected positively or negatively.

However, another negative impact that Argyrodes can have on its host is damage to the web. Some dewdrop spiders are known to actually eat the silk itself, and others create gaping holes in a snare when they actively remove prey to an area outside of the web where they can dine without fear of detection by the host.

Next time you come across a large orb web, take a minute to scan for dewdrop spiders. Our understanding of the relationships between Argyrodes and their hosts is still in its relative infancy, and observations you make and record could shed light there.

Sources: Grostal, Paul and David Evans Walter. 1997. “Kleptoparasites or commensals? Effects of Argyrodes antipodianus (Araneae: Theridiidae) on Nephila plumipes (Araneae: Tetragnathidae).” Oecologia, 111: 570-574.
Wise, D. H. 1982. “Predation by a commensal spider, Argyrodes trigonum, upon its host: an experimental study.” Jrnl. Of Arachnology, 10: 111-116.

Wasp Wednesday: Pachysomoides fulvus

2011-09-07T20:03:00.000-07:00

Sometimes, the worst enemy of a wasp is another wasp. Paper wasps in North America have much to fear from a stealthy little ichneumon wasp named Pachysomoides fulvus. I had the good fortune of finding one biding her time in the vicinity of a nest of Northern Paper Wasps, Polistes fuscatus in Adams County, Ohio last month.

This parasitic wasp ranges from New York to Florida, and west to California and British Columbia, but does not appear to be abundant anywhere.

The female wasp lays her eggs on larvae or pupae of paper wasps inside the cells of the exposed paper comb. Young nests populated only by the foundress are especially vulnerable since the “queen” must leave the nest to hunt food for her offspring. Interestingly, an image over at Bugguide.net appears to show one of these wasps ovipositing in the wall of a cell that has at most only an egg in the bottom. Perhaps the larval ichneumon would emerge once the larval paper wasp had hatched.

I found more detailed information on the life history of Pachysomoides fulvus difficult to come by online, at least without buying access to articles from journal warehouses like Jstor. I have also packed up all my books now in preparation for moving. I might revisit this unique wasp, and will alert you if I am able to add more.

There is a second species of Pachysomoides in the U.S. that bears the unfortunate name of P. stupidus. Considering it is willing to confront a population of much larger wasps, the epithet might be appropriate! P. stupidus occurs in the southeast, from North Carolina to Florida and Texas and southern Illinois. It is an ornate, black and white banded insect with orange legs.

In this species, the female wasp lays several eggs on a pre-pupal Polistes grub. The larvae that hatch from those eggs then feed gregariously as external parasites on the pupa. Because the larval paper wasp spins a silken cap over its cell before pupating, the parasitic ichneumon larvae can feed undetected by the adult wasps on the exterior of the nest. Up to thirty-one larvae have been observed on one paper wasp pupa (Pickering, 1980).

Sources: Pickering, John. 1980. Larval Competition and brood sex ratios in the gregarious parasitoid Pachysomoides stupidus. Macmillian Journals Limited.

Spider Sunday: Black and Yellow Argiope

2011-09-04T12:15:00.000-07:00

The Facebook page for SpiderIdentification.org is really busy these days. It is no surprise. Spiders in the northern hemisphere, especially orb weavers, are reaching maturity now. Larger spiders spin larger, more conspicuous webs, often in situations where people notice them more often. The chief attention-getter in the United States right now is the Black and Yellow Argiope, Argiope aurantia.

The females are very large spiders, with a body length of 19-28 mm. Their bright Rorschach pattern of black and yellow might set off your “dangerous arachnid” radar, but no orb weaver of any kind is considered by scientists to be dangerously venomous to people or pets. Males, by contrast, are tiny, only 5-9 mm in body length, and magnitudes smaller in terms of body weight. Females need to build up energy reserves to be able to produce eggs.

The female Black and Yellow Argiope spins a rather small orb web given her size, usually in tall grass or shrubs no more than two or three feet off the ground, and usually lower. There, her snare can intercept large insects like grasshoppers.

A distinctive signature in the webs of most Argiope species (there are at five species north of Mexico) is a thick, zigzag band of silk running down the center of the web. This structure is called a “stabilimentum,” and its function remains something of a mystery. It may serve to shield the young spiders, which confine the stabilimentum to the hub of the web, from harm. The young spider quickly zips to the other side of the web when it feels threatened. Another hypothesis is that the stabilimentum is like a beacon on a tall building: it advertises the presence of the web to birds in flight so that the avian animal won’t destroy the web by accident. This comes at a cost, however. The presence of a stabilimentum can reduce prey-catching success by as much as thirty percent (Blackledge and Wenzel, 1999). That statistic also flies in the face of yet another hypothesis: that the stabilimentum most likely functions as a lure. The silk band stands out bodly in the ultraviolet end of the light spectrum, and many insects seeking flower nectar may mistake it for a raceme of flowers. Not all individual spiders spin a stabilimentum, and one might assume that webs spun higher in the vertical plane would be more likely to have one if the purpose was to deter bird strikes.

Look for male spiders lurking on the outskirts of a female’s web. They may be attracted to the female by a pheromone she emits (Olive, 1982). Approaching cautiously, a male may eventually be able to couple with the gargantuan object of his affection. He inserts one of his pedipalps into one side of the female’s epigynum (female external genitalia), and quickly pumps his sperm into her, hopefully before she renders him a meal. He will repeat the process with his other pedipalp on the opposite side of the female’s epigynum, if he is able. Should he succeed even once, he usually breaks off the tip of the pedipalp, which remains stuck in the epigynum. This “mating plug” therefore prevents any competing male from inserting into that opening (Foellmer, 2008).

Once mated, a female produces one or more egg sacs, each about the size of a large marble, and covered in tough, papery silk. Inside are 300-1,400 eggs. The eggs hatch in late autumn or early winter, but the spiderlings do not exit the egg sac. Instead, they go into diapauses, a dormant state with lowered metabolism. They emerge the following spring and reach adulthood by late summer. Various parasites and predators can take their toll on the egg sacs and spiderlings, however. One study found that 19 species of insects and 11 species of other spiders emerging from the egg sacs of Argiope aurantia. Chief among the parasites were the ichneumon wasp Tromatopia rufopectus, and the chloropid fly, Pseudogaurax signatus. The overwhelming predators of the egg sacs are birds. Nearly every egg sac found in the wild during the study had suffered damage from birds (Lockley and Young, 1993).

The Black and Yellow Argiope is also known as the “Writing Spider,” named perhaps for the stabilimentum, Golden Orb-weaver, and Yellow Garden Spider, among other aliases. I grew up learning it as the “Golden Garden Spider.” The species ranges from coast to coast in the United States, but is absent from arid regions.

Enjoy your encounters with these remarkable spiders while you can. The first frost is likely to claim their lives, if they do not perish in some other way before that date. See if you can determine what kinds of insects they are preying on, and whether their web location changes. There remains much to learn about even our most common and conspicuous arthropod neighbors.

Sources: Blackledge, Todd A. and John W. Wenzel. 1999. “Do Stabilimenta in Orb Webs Attract Prey or Defend Spiders?” Behavioral Ecology. Vol. 10, No. 4, pp. 372-376.
Foellmer, Matthias W. 2008. “Broken genitals function as mating plugs and affect sex ratios in the orb-web spider Argiope aurantia.” Evolutionary Ecology Research. Vol. 10, pp. 449-4462.
Lockley, T. C. and O. P. Young. 1993. “Survivability of Overwintering Argiope aurantia Egg Cases with an Annotated List of Associated Arthropods.” Journal of Arachnology. Vol. 21, No. 1, pp. 50-54.
Olive, Cader W. 1982. “Sex Pheromones in Two Orbweaving Spiders: An Experimental Field Study.” Journal of Arachnology. Vol. 10, No. 3, pp. 241-245.

An Entomologist in Hollywood?

2011-09-02T13:25:00.000-07:00

Yesterday I applied to be a host for a new television series being produced by Asylum Entertainment "and a major cable network." Wish me luck. I did share the link to my YouTube demo reel, but I fear they may think I'm not animated enough. I'm no Steve Irwin, but I am no stick in the mud, either. Maybe they will notice the stand-up performance in my YouTube account....

I have a gut-level feeling this is a more legitimate media venue than some of the other opportunities that have crossed my desk, so I really want to make it to the next level in the audition process. My style is to deliver accurate information, allay fears, refute urban legend and folklore, and do so with empathy to those not as sympathetic to the arthropod realm as I am. There have been far too many over-the top hosts already.

Stay tuned, and feel free to offer your support here, on Facebook, and any other public outlets you can think of. Thank you.

Wasp Wednesday: Wasp Workshop

2011-08-31T07:00:00.000-07:00

I recently had the privilege of leading a wasp identification workshop at the ultra-modern Eulett Center in Adams County, Ohio. The ten participants arrived Friday evening, August 26, at the nearby rustic lodge known as Rieveschl Chalet. Both facilities are run by the Cincinnati Museum Center, though The Nature Conservancy also occupies offices in the Eulett Center and the two organizations co-manage the Richard and Lucile Durrell Edge of Appalachia Preserve System.

All my “students” were enthusiastic and energetic in the field and in the lab. I gave an introductory lecture on selected wasp families at the Chalet on Friday night, and we looked forward to seeing actual living specimens in the rural and prairie habitats the next morning.

There are never any guarantees that one will actually find wasps just by looking, but my hosts Chris Bedel and MarkZloba and myself scouted out some nearby areas ahead of time on Friday. That paid off. The participants got to see the Katydid Wasp, Sphex nudus, nesting in the dirt floor of an old barn. We even witnessed one of the wasps fly in with her prey, a Carolina Leaf-rolling Cricket (Camptonotus carolinensis).

We also discovered caterpillars of the Catalpa Sphinx moth, Ceratomia catalpa, covered in the cocoons of the parasitic braconid wasp Cotesia congregate. These and other wasps we observed will be topics in future “Wasp Wednesday” posts, and images shared on my Flickr Photostream.

We convened at the Eulett Center for lunch, then went back out for a more field time at another location. There we collected cuckoo wasps (family Chrysididae), and observed a mating pair of thread-waisted wasps, Eremnophila aureonotata. Inside a barn we saw many old nests of the Pipe Organ Mud Dauber, Trypoxylon politum, and an active nest of the Northern Paper Wasp, Polistes fuscatus. When wasps were not to be found, the sharp eyes of the group spied many other insects including bizarre caterpillars like the “Monkey Slug.”

The late afternoon was spent attempting to learn the complicated anatomy of wasps, and introducing “keys” as a way to identify wasps to family, genus, and sometimes species. Traditional keys are dichotomous, meaning that they are composed of a series of couplets. One reads each couplet and decides which of the two lists of characters corresponds to their specimen, then proceeds to the next indicated couplet. Eventually, this process yields a name instead of another couplet. Interactive keys are a product of internet technology whereby the user checks boxes that correspond to their specimens, then hits the search button to whittle down the possibilities.

Chris Bedel, in addition to having a wealth of knowledge about the local flora and fauna, is a fabulous cook. Dinner on Saturday night was healthy and delicious: Pasta with artichoke hearts, cherry tomatoes, black olives, chicken, and spices, plus a mixed greens salad, garlic bread, and brownies and ice cream and strawberries for dessert choices.

After dinner we played a game I invented called “Wasp/Not Wasp,” whereby students view two images on one PowerPoint slide. They must determine which is the wasp, and what the other insect imposter is. I complicate matters by sometimes showing two wasps, or two non-wasps. The whole thing seemed to be a hit, and most of the time everybody got the answers right.

I concluded the evening with a short lecture on wasp sleeping behavior.

Sunday morning found us afield again, this time in the Lynx Prairie unit of the preserve system. Mark Zloba had set up an enormous malaise trap days before, to help secure wasp specimens. A malaise trap is a tent-like structure designed to intercept flying insects. The “bugs” then try to fly over the barrier. Instead they are funneled to the highest point (at both ends of the trap in this case) where they drop into a container with a killing agent. This trap is often one of the few ways one can capture certain kinds of Hymenoptera, and indeed the diversity just in the one sample was amazing.

Before we knew it, the morning was over and it was lunchtime. After a leisurely meal, the students slowly departed to resume their normal lives, as if having an interest in nature and insects means you have a “normal” life. I had a great time seeing friends I haven’t seen in decades, meeting Facebook friends, and making new friends that I know will be lifelong colleagues.

Special thanks go to Stephen Pelikan who drove me out to the Eulett Center from the Cincinnati International Airport. Chris and Mark were exceptional hosts that made me feel instantly at home. They made modest demands, and allowed me ample time to explore on my own.

Do consider attending Advanced Naturalist Workshops like this, or simply visiting the Eulett Center on your own. They always welcome visiting naturalists, researchers and scientists who give them ample warning.

Spider Sunday: Crevice Weavers

2011-08-28T07:00:00.000-07:00

Perhaps no spiders are more often misidentified than the “crevice weavers” in the genus Kukulcania, family Filistatidae. They are quite common throughout the southern United States, where they are frequently confused with everything from brown recluse spiders to tarantulas.

There are currently five species and one subspecies of Kukulcania recognized in the U.S. Here in Arizona we have both K. arizonica and K. hibernalis (the “Southern House Spider”). Indeed, houses are often where you find them. Look for their sprawling, lacy webs issuing from the exterior of window frames, under the eaves, and similar situations.

Filistatids in general belong to a larger group of arachnids called “cribellate” spiders. These spiders possess an extra silk-spinning organ called a cribellum, and a comb on the outside of the metatarsal segment of each fourth leg. This row of short, stout, curved hairs is called a calamistrum and is used to “fluff” the silk that issues from the plate-like cribellum. This “carding” of silk is accomplished by very rapid vibration of the fourth leg as it rests on the third leg. This is in contrast to most other cribellate spiders that employ a slow rocking motion. The web that results is therefore not sticky, but the threads so random that they easily entangle potential prey.

The odd web is just the beginning of weird for Kukulcania crevice weavers. The genders differ so dramatically in appearance that one can be forgiven for assuming they are different species. Mature females are a lovely, velvety black or dark gray in color, with a body shape and lumpy eye arrangement reminiscent of a tarantula. Mature males are beige or pale brown in color, with small bodies and extremely long legs. They are mistaken for brown recluse spiders much of the time, but note the differences. Male Kukulcania have eight eyes, grouped atop the crown of the head as they are in the female. Recluse spiders have only six eyes, grouped in three pairs across the front edge of the carapace. Also notice the extremely long, elbowed pedipalps of the male crevice weaver. No recluse spider is that….well,…well-endowed.

We’re not finished, it gets stranger. All filistatids known thusfar have their jaws (chelicerae) fused. That means that each one of the pair is incapable of moving independently, like in most other spiders. They are also built to lose their legs if necessary to escape a predator. Actually, many kinds of spiders possess the ability to break off parts of their legs without losing much blood in the process. This phenomenon is known as “autospasy,” and in the case of crevice weavers the weak joint is at the juncture of the tibia and patella segments.

Interestingly, female Kukulcania continue to molt after they become adults. Mygalomorph spiders (tarantulas) are the only other spiders known to do this. It seems to be related to longevity: both spiders take a long time to reach sexual maturity, and are capable of living several years. Like the cellar spiders I addressed in an earlier blog entry, filistatids are “haplogynes,” meaning that the females have largely unmodified, if not non-existent external genitalia. The paired openings to her reproductive tract are under what is more-or-less a slot-like orifice.

The best time to observe Kukulcania species is after dark. Females will venture to the lip of their retreat in anticipation of prey. Males will be wandering in search of love and romance. See if you can’t find one or both of the sexes on the exterior of your own home, garage, shed, or barn.

Wasp Wednesday: Pimpla sanguinipes

2011-08-24T21:52:00.000-07:00

I should know by now that nothing comes easy in entomology. Here I figured I could just whip out a short piece on an ichneumon wasp I imaged in southern California back on March 26, but no-o-o-o, it looks like even the name I have for it, courtesy of Bob Carlson via Bugguide.net, might be outdated. Meet Pimpla sanguinipes, or whatever alias it goes by these days.

Actually, it looks like the appropriate name for this member of the family Ichneumonidae is Coccygomimus sanguinipes. Bugguide lists Coccygomimus as a “synonym” for Pimpla, so maybe it still *is* Pimpla.

The wasp I found at the salt marsh preserve in Carpenteria is further defined by the subspecies name erythropus. I do wonder what all these references to “blood” mean, though the wasp does have reddish-orange legs.

Dr. Carlson pointed out the complexity of all this in a personal communication with Vasile Bagazzoli, a volunteer editor at Bugguide:

"erythropus and sanguinipes might really be two separate species, judging from the fact that they occupy different habitats: sanguinipes in arid areas and erythropus in forested areas. Townes even had differences in punctation for the two. His concept of subspecies was very dubious, and he did not strictly apply the concept in a geographical sense and named many sympatric subspecies, many of which I relegated to synonymy in the 1979 catalog. But this case was different, and I might have just elevated the two taxa to species level but did not. I don't remember if I had a reason for not doing it, but maybe it was because there was a dearth of specimens in the National Collection from which I could form an opinion."

Dr. Carlson is retired from the Systematic Entomology Laboratory at the National Museum of Natural History in Washington, DC. He also studied under the “grandfather” of ichneumon taxonomy, Henry T. Townes.

Ok, back to the actual wasp, and what *it* does for a living. The species ranges west of the Rocky Mountains from Idaho to New Mexico and west to the Pacific coast including British Columbia and southern California.

Females seek out moth caterpillars in which to lay their eggs. Their hosts include tent caterpillars (Malacosoma spp.), buck moths (Hemileuca sp.), the Virginia Tiger Moth (Diacrisia virginica), the Douglas Fir Tussock Moth (Orgyia pseudotsugata), Western Tussock Moth (O. vetusta), Coddling Moth (Cydia pomonella), Genista Broom Moth (Uresiphita reversalis), Gooseberry Fruitworm (Zophodia convolutella), Barberry Geometer (Coryphista meadii), the Oak Looper (Lambdina punctata), and two other geometer moths (Eucaterva variaria and Prochoerodes forficaria). Several of these moths are abominable pests, so this generalist parasite is a welcome friend to agriculture and forestry.

The physical dimensions of this wasp don’t fit its superhero reputation. Females range between 10.5-12.5 millimeters in length, males around 8.5 mm. The black body, orange legs, and short, stout ovipositor help to identify the species fairly easily. We just can’t decide what name to call it.

Spider Sunday: The Cross Spider

2011-08-21T07:00:00.000-07:00

’Tis late summer, now, in most parts of North America, anyway, and orb weaver spiders are becoming more conspicuous as they mature into large adult specimens and spin bigger webs (soon to be revealed by falling autumn foliage). Among the most abundant of these spinners is the “Cross Spider,” Araneus diadematus.

The Cross Spider is a European immigrant, just like most of us human residents of the U.S. and Canada, so the species feels most at home in northern climes. It is recorded from Newfoundland and Nova Scotia to British Columbia and south to northern California, Michigan, Ohio, Pennsylvania, New York and Rhode Island. It is plenty accustomed to people, too, so it is a regular occupant of gardens and yards in urban areas.

Araneus diadematus gets its popular English name not from an angry disposition, but because it usually sports silvery-white dots that form the pattern of a traditional Christian cross on its abdomen. This is a relatively consistent marking, but as with most orb weavers, there can be exceptions. The spiders usually hang head-down in the very center (hub) of their webs, but sometimes an individual spider may be more reclusive, and connect herself to the web via a bundle of “signal threads” that run from the hub to her hiding place in a rolled-up leaf or other nearby retreat.

The reaction of homeowners to the presence of this and other species of orb weavers runs the gamut from curiosity to consternation. No species of orb weaver is known to be dangerously venomous to people or pets, so there is no reason to fear them. The spiders themselves will literally shake at the close approach of a person or other large animal, vibrating their web and no doubt startling the inquisitive visitor. Should that tactic fail, most orb weavers drop abruptly from their web, anchoring a dragline to the hub so they can climb back up once danger passes.

This species happens to include some real celebrities. No, seriously. “Anita” and “Arabella” were two female Cross Spiders sent into space on Skylab 3 in 1973 to study the effects of zero gravity on web construction. Prior to that, several specimens were used as guinea pigs in the study of how psychoactive drugs affect spiders’ ability to spin webs. Those experiments were first conducted by a German scientist beginning in 1948, then repeated by NASA scientists in 1984. For an absolutely hilarious send-up of that research, you must see ”The Wood Spider” video on YouTube. I take no responsibility for laughter-induced fatalities.

An adult female Cross Spider has an average body length of about 13 millimeters, though gravid females certainly appear larger. Like the story of Charlotte’s Web, each spider’s life from egg to adult spans only a year. Enjoy their handiwork and pest-controlling services while you can.

Welcome Birds & Blooms Readers!

2011-08-18T23:45:00.001-07:00

I am honored to have this blog profiled online by Birds & Blooms magazine as their "blog of the week" today.

Please let me know what kind of entries you would like to see here in the coming months. Perhaps you want to know more about certain kinds of butterflies, or have always wondered what that strange animal is that behaves like a hummingbird but looks like it has a lobster tail (psst: it is a sphinx moth).

Your garden or backyard is a fascinating urban habitat for many insects and arachnids that you probably never see, but that play a significant role in pollinating your plants, keeping pest insects in check, and making rich compost for you to use in fertilizing your flowerbeds.

I look forward to making this your "go-to blog" for solving your garden "bug" mysteries. Thank you for visiting, I hope you will come back again.

Wasp Wednesday: Beewolves

2011-08-17T07:00:00.000-07:00

I was mistaken the first time I thought I saw a beewolf. It turned out that I was seeing a cuckoo bee in the genus Nomada. The real deal, the beewolves of the wasp genus Philanthus, are truly complex for solitary wasps. The most common species in North America is P. gibbosus, found from the Atlantic to the Pacific, and Canada to Mexico.

The European beewolf, Philanthus triangulum, which preys on honeybees, gained fame as one of the research subjects of Nikolaas Tinbergen, a Dutch animal behaviorist (ethologist) who shared the 1973 Nobel Prize in Physiology or Medicine. Tinbergen coined the name “beewolf,” and demonstrated that the female wasp was able to locate the buried entrance to her burrow by using subtle landmarks as cues. Our P. gibbosus does so as well. Meanwhile, we can’t remember where we parked our car.

A single female P. gibbosus usually excavates in bare, coarse sand, sandy-clay, or sandy loam soil, often removing small pebbles as she goes. A typical burrow extends for 15-24 centimeters, beginning as an oblique tunnel that eventually becomes horizontal. Some burrows may reach a length of a meter or more, but these may represent expansion of an existing nest by the succeeding generation. Individual cells at the end of very short tunnels radiate from the main burrow along its length.

Beewolves earn that name. The females target small bees, and even other wasps, as food for their larval offspring. Not all beewolves you see around flowers are there for nectar. The females will actively stalk bees that are busy gathering nectar and pollen themselves. A distracted bee could be a dead (well, paralyzed) bee.

Philanthus gibbosus is a well-studied insect, and has been recorded taking 35 species of bees and wasps as prey. The majority of victims are “sweat bees” in the family Halictidae, but also yellow-faced bees in the family Colletidae; and a couple members of the family Andrenidae. There are also records of aphid wasps in the family Crabronidae, genus Pemphredon falling prey.

A victim is stung immediately between its front legs, disabling a nerve center and rendering the bee paralyzed. The wasp then carries the bee beneath it, held in the wasp’s middle legs. It takes several bees to feed one larval beewolf wasp.

Male beewolves are highly territorial, perching on low twigs or leaves where they can intercept a female or chase off a competing male. Males also scent mark twigs and foliage, employing brushes of hairs on the underside of the abdomen to “paint” an odor that communicates their individual ownership of a small area. Their possession of a territory is usually short-lived, however, as competing males frequently displace resident individuals.

Interestingly, Philanthus gibbosus is known to engage in burrow sharing, whereby sibling females may occupy their birth nest for a short time before dispersing. There is also evidence that sibling females may expand their birth nest for at least one generation, depending on the condition of the burrow. This tendency toward sociality might be more of a population-level phenomenon than a behavior typical of the entire species.

One or more males may also spend nights, and periods of inclement weather, in the burrows of females. Males tend to be return to the same burrow each night.

Invincible as they might appear, beewolves are not immune to their own enemies. P. gibbosus is plagued by a host of adversaries, especially “satellite flies” in the genera Metopia, Senotainia, and Hilarella. The female flies follow female beewolves back to their nests, then deposit larvae at the lip of the entrance. The larvae crawl down the tunnel and become parasites of the larval wasps. The velvet ant Dasymutilla nigripes is likely a parasite as well; and the cuckoo wasp Hedychrydium dimidiatum is another suspect parasite. Adult beewolves can be killed by crab spiders lurking in flowers, and by robber flies that take advantage of the slow flight of prey-laden female wasps.

Beewolves are members of the family Crabronidae, and the subfamily Philanthinae. Worldwide there are about 136 species, about 30 of which occur in North America. The majority are rather diminutive insects, only ten millimeters or less in body length. They usually sport ornate patterns of black and yellow or white, the males with all-pale faces and no “tarsal rake,” the spines on the front legs that help the females dig.

Source: Evans, Howard E. and Kevin M. O’Neill. 1988. The Natural History and Behavior of North American Beewolves. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 278 pp.

Spider Sunday: Arizona Blonde Tarantula

2011-08-14T07:00:00.000-07:00

Without a doubt, one of the iconic animals of the Sonoran Desert is the tarantula. What would a Western, or desert horror movie be without a shot of one of these giant spiders moving leisurely across the landscape? Maybe a tumbleweed, too, though a Russian Thistle moves faster than a strolling tarantula.

Tarantulas belong to the family Theraphosidae, and only the genus Aphonopelma is native to North America. There are 54 currently recognized species north of Mexico, and determination to species level is complicated by the fact that these are primitive animals in the evolutionary sense, with simple genitalia that don’t allow for easy comparison. That said, the most common species here in southern Arizona is the “Arizona Blonde,” Aphonopelma chalcodes.

It is mature male spiders that are most often seen crossing roads, especially at night, during the summer monsoon season. The male is easily recognized by his relatively lanky appearance, with a smaller abdomen and longer legs than the female. His front legs also have a spur on the underside of the tibial segment. The spurs are used to hold the female’s fangs at bay during mating. His coloration also differs from that of the female. His legs are entirely black, while the female has black femur segments with the remaining leg segments brown.

Both sexes live in burrows in the ground. Females rarely venture out, lest they become even more vulnerable to tarantula hawk wasps, and other predators such as coatimundi. An occupied burrow will have a thin curtain of silk over the entrance during the daytime. The spider will sit at the lip of its tunnel during the night, the better to ambush any unsuspecting insect or other small animal that comes within striking range. During the winter months the spiders plug their burrows with soil. Fat reserves sustain the spider during those lean months.

Tarantulas begin life as surprisingly small spiders, like the one below. Margarethe Brummermann found this specimen under a cow patty near Sunsites in the Dragoon Mountains. It takes a minimum of seven years for a tarantula to reach sexual maturity, and that is for captive specimens that receive regular meals and are otherwise provided with optimal conditions.

The black patch on the abdomen of the spiderling indicates special hairs that tarantulas use in self-defense. Rather than striking at an adversary with their fangs, our North American species literally kick themselves in the rear. Be careful if you see a tarantula doing this. It is dislodging short, microscopically barbed hairs that easily become airborne. These hairs, if they contact mucous membranes of the nose or eyes, cause extreme irritation. Some people may also have an allergic reaction, including a rash or other inflammation of the skin. Even a molt (shed “skin”) of a tarantula can bring about an allergic reaction in those people who are susceptible.

Tarantulas are among the very few spiders that continue molting after they reach adulthood. This process helps replenish those defensive hairs, and shed mites, other parasites, and dirt. Captive female spiders like the one shown above have been known to live as long as thirty years, but “wild” specimens likely don’t survive nearly as long. Males, after reaching adulthood, abandon their burrows in search of mates. After successfully breeding they usually die.

Members of the genus Aphonopelma are collectively distributed west of the Mississippi River and as far north as Missouri, Colorado, Utah, Nevada, and the southern two-thirds of California.

Life Cycle of a Leaf Beetle

2011-08-12T07:00:00.000-07:00

Leaf beetles of the family Chrysomelidae seem to be particularly diverse here in southern Arizona. One of the most common species is Leptinotarsa lineolata, a relative of the familiar Colorado Potato Beetle. A visit to one arm of the Sonoita Creek State Natural Area in Rio Rico, Arizona on July 31 found this beetle in profusion, and all life stages but the pupa present.

The adult beetles are about 7-8 millimeters long, but colorful. The head and thorax are metallic green, while the elytra (wing covers) are ivory with black streaks. The beetles and their larvae feed exclusively on Burrobrush (Hymenoclea monogyra). The beetles become numerous after the onset of monsoon rains, usually in early or mid-July. They quickly set about reproducing.

Once mated, the female beetles lay eggs in rows along the edge of a leaf near its tip. The large numbers of eggs and their bright yellow color make them very conspicuous.

Larvae hatch from the eggs in about seven days and commence feeding on the burrobrush leaves. The grubs go through four instars (intervals between molts) before pupating. I assume the large larvae I imaged are fourth instar. The larvae probably sequester the toxins in the plant to use in their own chemical self-defense. That would explain the bright black, white and yellow markings reminiscent of Monarch butterfly caterpillars. Such toxic insects tend to advertise their unpalatable nature through “warning colors,” a phenomenon known as aposematism.

Well, no wonder I couldn’t find the pupal stage. An unpublished study by Ross Arnett and Richard L. Jacques in 1971 followed L. lineolata through its entire life cycle, and they found that pupation occurs in the soil. Adult beetles emerged from the pupae roughly ten days later.

According to Michael Plagens’ account of this species, the beetles are capitalizing on disturbed riparian zone habitats where their host plant thrives in the wake of cattle grazing. Burrobrush is toxic to mammals, so livestock leaves it alone while eating competing vegetation.

Leptinotarsa lineolata ranges from Texas to California, and south into Mexico. There is no missing this insect if you are at all observant and in the right habitat at the right time. Check them out!

Source: Jacques, Richard L., Jr. 1988. The Potato Beetles: the Genus Leptinotarsa in North America (Flora & Fauna Handbook No. 3. Gainesville, Florida: Flora & Fauna Publications. 147 pp.

Wasp Wednesday: Western Cicada Killer

2011-08-10T07:00:00.000-07:00

According to my friend Margarethe Brummermann, this has been the year for cicada killer wasps in southern Arizona. I have spent much of my summer traveling to other parts of the U.S. though, so I’ve missed a lot of the action around Tucson. Plus, cicada killer abundance tends to be very localized. Couple this with the spring drought and the fact that I live in the city itself where there is little greenspace, and it is no wonder I have seen few insects. However, a visit to Tohono Chul Park back on June 17 did allow me a glimpse of a female Western Cicada Killer, Sphecius grandis.

As its scientific name implies, this is a large, magnificent animal. Separating this species from the nearly identical Pacific Cicada Killer is not easy, but I have observed a semi-reliable trait to tell the two apart. The abdomen of the Western Cicada Killer has pale bands along the entirety of its length, whereas the Pacific Cicada Killer has the bands terminating well before the tip of the abdomen. The Pacific Cicada Killer also tends to have much more of a contrast between the dark reddish brown and pale yellow coloration.

The only truly reliable means of discerning the two species is by the punctation of the first two abdominal segments, as illustrated in the online key to cicada killers by Charles Holliday. This requires extremely close examination of the wasp, though, and a live specimen won’t hold still for that.

Sphecius grandis ranges throughout much of the western United States, from Kansas and Nebraska south to Texas and west through Nevada to California, Idaho, Oregon, and southeast Washington. I am hoping that I can find this species in Colorado next summer.

Like the majority of cicada killer species, the Western Cicada Killer likes to nest near other members of its kind. This was graphically demonstrated to me last summer when John Rhodes of the Sonoran Arthropod Studies Institute invited me to his neighborhood where a number of S. grandis were nesting in the bank of a dry wash. Ironically, the date was June 17, 2010, exactly one year to the day prior to my next sighting at Tohono Chul. John’s place sits in the lower foothills of the Santa Catalina Mountains and the male “Cactus Dodger” cicadas, Cacama valvata, were singing loudly from seemingly every branch of mesquite and palo verde trees.

The one thing the cicadas could not dodge were the cicada killers. Just standing in the wash and looking up and down it I could see female wasps flying in with their prey. It is a jaw-dropping sight to see a large wasp, carrying an equally large prey insect, droning along like it has no burden at all. That would be like you or I running full speed while carrying a sofa.

The wasp has perhaps her greatest challenge in shoveling her prize through the entrance to her burrow. Once inside she will cart the cicada, paralyzed but alive, into a previously-prepared cell near the bottom of the tunnel. This will be the cicada’s death chamber, as it is destined to become food for one of the female wasp’s larval offspring. She will cache one or two cicadas in each of the several underground cells before sealing the entire burrow and beginning a new nest.

Cicada killers do visit flowers to refuel on nectar, but they are not commonly seen on blossoms. They will also sip sap oozing from wounded trees and shrubs. Male cicada killers are territorial, and will perch where they can oversee a nesting aggregation of females. They aggressively challenge all intruders but, since they have no stingers, it is all bark and no bite.

Enjoy watching these wasps if you have them on your property. Their nesting activity lasts at most about a month, and as long as you don’t walk barefoot through the area they occupy, risking stepping on a female wasp, you need not fear.

Spider Sunday: Desertshrub Spiders

2011-08-07T07:00:00.000-07:00

The deserts of the American southwest are harsh, demanding environments. Consequently, they host a unique spider fauna. Among the more common of these endemic arachnids are the desertshrub spiders in the family Diguetidae. They might easily be mistaken for funnelweb weavers or labyrinth spiders at first glance, but with a little practice one can recognize both the spider and its web fairly easily.

Diguetia is the only genus in North America, with seven species occurring north of Mexico. They have collectively been recorded from Utah and Colorado to California, and Texas. D. canities is the most widely distributed species, and has been separated into three subspecies.

These are mid-size spiders, mature individuals topping out at 5-10 millimeters in body length. Their color and pattern is very reminiscent of spiders in the family Agelenidae, and their webs might reinforce that misconception. The webs are horizontal sheets, slightly dome-shaped, with a central tubular retreat in the vertical plane above the sheet. There is also a tangle of threads on all sides of the sheet, above and below. The spider travels on the underside of the sheet to attack prey caught in the tangled threads.

My experience has found that populations of these spiders are rather localized: where you find one web you will find several others nearby. They are mostly located less than two feet off the ground, frequently amid the spiny pads of prickly pear cacti (Optuntia spp.). The retreats are shrouded in plant debris, remains of prey insects, and may include the camouflaged egg sacs of female spiders. These conical “houses” are often the first thing you notice, before the rest of the web comes into focus.

The desertshrub spiders are relatively primitive in the evolutionary sense, and are classified as “haplogynes.” This means the female’s genital opening lacks a hardened plate, and the male’s pedipalps (used in mating) are rather simple. Tarantulas and cellar spiders are more familiar examples of haplogyne spiders.

Next time you are out in the desert, keep an eye out for the webs of desertshrub spiders. The snares are roughly four to six inches in diameter, so are not too easily overlooked.

Wasp Wednesday: Black & Yellow Mud Dauber

2011-08-03T07:00:00.000-07:00

Few wasps in North America are as ubiquitous and conspicuous as the familiar Black and Yellow Mud Dauber, Sceliphron caementarium. Even when the wasps themselves are not obvious, their mud nests are often are. Homeowners consider the amorphous clod-like nests to be eyesores, if not a hazard when the female wasp is at work on one. Take a closer look, and you will be amazed by the wasp and her legacy of insect lodging.

Sceliphron caementarium has an extraordinarily widespread geographic distribution, and varies markedly in its appearance from north to south. Northern specimens tend to be mostly black, with dark, violaceous wings. Western specimens tend to be more yellow, with yellow wings.

Not only does this species occur from Canada to Central America and Peru, it has been introduced to the West Indies, Bermuda, Hawaii, the Marshall Islands, Cook Islands, Society Islands, New Caledonia, Australia, Fiji, Samoa, France, and Germany. Once again, international commerce has played a role in the wasp’s seemingly jet-setting lifestyle. Females may build nests inside of shipping containers that then make landfall at various ports.

Why does the Black and Yellow Mud Dauber succeed wherever it finds itself? The female wasps are generalist hunters of spiders, and spiders can be found everywhere as well. The wasp first finds a place to build her nest, usually in a sheltered situation such as beneath a rock overhang. Once she establishes a suitable location, she flies off to a patch of mud and rolls up a ball with her jaws and front legs. She then flies off with this pea-sized load and plasters it to the construction site she chose earlier.

Once she has laid down a layer of mud on the surface of the substrate, she begins fashioning a three-dimensional cell. Each subsequent load of mud makes a “rib” that reaches across half the span of the cell she is building. The arcs from either side meet at the middle, dovetailing nicely with each other and the adjacent ribs on the same side. Once the cell is completed, leaving an opening at one end, she may plaster more mud over the ribs, obliterating the initial artistic appearance of the cell.

A finished cell is then provisioned with paralyzed spiders captured by the wasp. She uses her sting to subdue her prey, but does not kill it. A comatose spider won’t spoil before her larval offspring has a chance to feed on it. Many spiders are harvested and packed into the cell. The wasp usually lays an egg on the first spider to go into the cell. Orb weavers and crab spiders seem to make up the bulk of prey, but the wasps are opportunists and will not hesitate to take other kinds of spiders.

Most female mud daubers make more than one cell, the next one placed immediately beside the previous one. The whole series of cells may then be covered in mud, making it look like some mischievous teenager hurled a clod onto a wall. Not very pretty, but an effective fortress against parasites.

And do mud daubers ever have parasites! Chief among them are the cuckoo wasps of the family Chrysididae. These little metallic jewels wait for the hard-working mud dauber to go off on the hunt again, then enter the nest and lay an egg inside. Should the mud dauber catch the intruder, the cuckoo wasp roles into a tight ball, its dense cuticle impervious to the stings and bites of its irate host. Chrysis angolensis is an African species now well-established in North America, but there are native species that attack the mud dauber, too.

Other enemies of the Black and Yellow Mud Dauber include ichneumon wasps in the genera Acroricnus and Osprynchotus, as well as chalcid wasps in the genus Melittobia, velvet ants in the genus Sphaeropthalma, and bee flies in the genus Anthrax. “Satellite flies” in the family Sarcophagidae, genus Amobia, are also a threat.

Look at an old mud dauber nest and you can decipher what happened to the offspring. A large hole chewed out at the end of a cell means an adult mud dauber successfully emerged. Small holes along the length of the cell mean some kind of parasite came out instead.

Once the new generation of wasps have emerged, the nests can serve as shelters for other insects or, ironically, retreats for spiders. Other wasps use the ready-made mud cavities for their own nests. Mason wasps like Ancistrocerus tuberculocephalus will partition an old mud dauber cell into at least two cells of its own.

Carpet beetle larvae will clean up any old spider and insect parts left over from all the tenants, and eventually the old nest may weather away, or be torn up by a mammal hoping for a juicy wasp larva snack.

It is impossible to address the many fascinating aspects of mud dauber biology in a single blog, so expect me to revisit this species in the future. Meanwhile, go see if any mud daubers have been busy on your own property. Chances are, they have been.

Spider Sunday: Western Black Widow

2011-07-31T07:00:00.000-07:00

The first time I encountered a black widow was in the desert of eastern Oregon. I cannot recall the circumstances exactly, but I was rather awed, given that I had read about them but never seen one until then. Thanks to the book How to Know the Spiders, by B. J. Kaston, I learned the species found in the Pacific Northwest is the Western Black Widow, Latrodectus hesperus.

Eventually, I was able to easily identify black widow webs, even if the spider was not present. Black widow webs are large, three dimensional tangles of extremely strong threads. The whole web can easily occupy a cubic foot or more, and you can pluck the silken strands like guitar strings without them breaking. A funnel-like retreat is usually seen going into a rodent burrow, under a boulder, or some other cavity that would take heavy machinery to break into. Black widows do not want anything to do with larger animals. Only at night are you likely to see the spider out on her web.

Believe it or not, black widows begin their lives as largely *white* spiders. They lose the pale spots and stripes as they age, but because males mature more quickly, in fewer molts, they never lose their pale markings entirely. Even the immature spiders sport at least some semblance of an “hourglass” marking on the underside of their abdomen, so you can still identify them as widows. Since widows sit upside down in their webs, that hourglass marking is usually visible.

The Western Black Widow is the largest North American member of the genus Latrodectus. Females have a body length of 14-16 millimeters as adults, males 7-8 millimeters. Mature females usually lack any red markings besides the hourglass, and that may be broken or even wanting in some specimens. Some individuals may be chocolate brown instead of black.

Mature males are recognized by their swollen pedipalps, which resemble tiny boxing gloves located near the spider’s face. He uses these as intromittent sex organs that fit like a key in the “lock” of the female’s paired genital openings. Contrary to popular myth, the female does not always cannibalize her mate, though sex is a risky business for nearly all male spiders.

Mated females can produce several egg sacs in their lifetime, each containing up to 750 eggs. Few of the spiderlings that emerge will make it to maturity themselves, due to cannibalization by siblings and other natural hazards. Adult females can live more than a year, though.

Western Black Widows are able to secure surprisingly large prey. Their webs are designed to trap prey walking over the ground. When a victim stumbles into one of the sticky trip threads attached to the ground, the thread breaks and rebounds, yanking the potential prey animal into the main body of the web. The trip threads are so elastic and strong that even small vertebrates can be captured in widow webs. I personally witnessed a hatchling lizard struggling in a web. Yes, I intervened.

While black widows have no problem killing prey as imposing as large beetles, they flee rapidly when they sense a larger creature such as a human. The speed at which they can scramble back into their retreat is astonishing. I have had many a photo opportunity cut short when I accidentally bumped a thread.

The Western Black Widow is a very common spider found from extreme southern British Columbia south to Mexico and west to Kansas, Oklahoma, and Texas. It is particularly abundant in drier habitats such as deserts and prairies, though it can be encountered in more damp situations as well.

Because of the timid nature of widows, it is relatively easy to minimize the possibility of being bitten. Simply take these precautions:

Never leave clothing, shoes, or gloves outdoors overnight. A spider can seek shelter during that time.
Do not put your hands or feet where you cannot see into, such as holes and crevices, inside the mailbox, or behind large objects that have been in storage for awhile.
Carefully inspect firewood, houseplants, toys, etc being brought indoors from outside in case a spider may be hitchhiking on the object.
Do not walk barefoot outdoors, especially at night.

Reactions to bites from widows can vary considerably from one person to the next because immune system responses to envenomation are highly individualistic. The spider may not even deliver much, if any, venom. Still, they typical experience is excruciating. The venom is neurotoxic, meaning it affects the nervous system. This translates to triggering constant muscle contractions that result in severe cramps, especially in the abdomen, legs, and other large muscle groups. One friend of mine had back spasms for months following a black widow bite. One should always seek emergency hospitalization immediately, precisely because one cannot be sure how their body will react. Antivenin is available for treatment, though it is recommended as a last resort by most hospital physicians. Antivenin is produced from horse serum, which can carry its own complications including allergic reactions. Obviously, avoiding bites is preferable to treating them after the fact.

Black widows cannot be easily “controlled.” Contact insecticides have a very low probability of reaching a hidden spider, and killing one spider means it will soon be replaced by another anyway (prime web sites are a coveted commodity). Meanwhile, the spiders will kill plenty of pest insects that could potentially be more trouble than the spiders themselves. By all means, do inspect playground equipment and toys before allowing your children to play outdoors. It all comes back to vigilance and prevention. Take care, but value the work your spiders do.

The Germans Are Back

2011-07-29T07:00:00.000-07:00

The other day I came out of my apartment to find a piece of paper stuck in my screen door. I was dreading reading about a rent increase, but the announcement was unpleasant in a different way. “We are starting a new program here at (name of apartment complex)” began the notice. Turns out that the management is initiating an ongoing pest control schedule, no doubt due to someone complaining about German Cockroaches, Blatella germanica.

I have had German roaches in my own apartment previously. Initially I did not treat for them because a Mediterranean House Gecko, Hemidactylus turcicus, had also taken up residence in my kitchen and kept the roach population to tolerable levels. Eventually, the lizard died, and then the roach population exceeded my psychological and physical “carrying capacity.”

I reluctantly purchased some roach bait traps, and that did the trick….until a few months ago, when I saw another roach. In the last month I have killed two: a male and a female. Still, I have a hard time with the invasion of privacy that comes with an extermination service, not to mention having some trepidation over whatever chemical treatment they are applying.

Ok, enough about me, how about some background on the German Cockroach? It is believed that most of our “domiciliary” roach species are native to tropical Africa, and can only exist outside their normal geographic range by occupying buildings that offer a year-round approximation of their tropical homeland. Why are they called “German,” then? Well, here in the United States at least, we have a history of naming economic pests after nationalities that we have had conflicts with. So, given our World War II enemies, it seemed fitting to apply the “German” epithet to this particular roach species (in Germany the species is called the “Russian” Cockroach).

The German Cockroach is one of the smaller roach species, ranging from 11-13 millimeters in length. Consequently, it is sometimes mistaken for some other kind of insect and dismissed. There is no ignoring their numbers, however, and opening a cupboard can send dozens of them scurrying for darkness in a dwelling that is infested with them. Males are sleek, slender, amber-colored insects, while females tend to be darker and more robust. Both genders are shown in the images here. See if you can tell which is which.

As far as I am aware, domestic pest roaches have only been implicated in the mechanical transmission of bacteria, never actually proven to be carriers of Salmonella and other treacherous microbes. Roaches groom themselves constantly, lest they themselves become victims of pathogens and fungi. This is not to say that cockroaches are at worst a nuisance. Far from it.

What has been conclusively demonstrated is that cockroach body parts, shed exoskeletons (remember roaches have to molt to grow), and fecal matter are a major, major trigger of asthma, especially in children. This is one reason that neglect of public housing should be a crime: improper maintenance can lead to chronic health issues that are far more costly to society (and the individual) in the long run. Also, entomologists who study roaches in the lab frequently develop allergies to roach exoskeletons, feces, and body parts. Such afflictions are sometimes severe enough to cause the scientists to abandon roaches as study subjects.

Cockroaches are successful organisms for several reasons. They achieved near perfection in the evolutionary sense millions of years ago, judging by the fossil record of roaches that are essentially identical to contemporary species. They are generalist feeders, able exploit all manner of organic matter. They are adept at detecting and avoiding poisons, being able to taste-test food before ingesting any. They reproduce at a rate that makes rabbits envious.

Female German Cockroaches cannot be accused of parental neglect. Once mated, a female will produce an egg capsule called an “ootheca.” Each ootheca contains an average of 30-40 eggs. The female carries the capsule at the tip of her abdomen until just before the eggs are ready to hatch. Then she carefully deposits the egg case in a crack or crevice where the cockroach nymphs can emerge in relative safety. Each female roach can produce several ootheca during her lifetime.

A typical roach population is a youthful one, comprised of about eighty percent nymphs of various stages and twenty percent adults. I haven’t seen any nymphs in my home lately, and I hope it stays that way.

Wasp Wednesday: Ancistrocerus tuberculocephalus

2011-07-27T07:00:00.000-07:00

I can always count on an aphid-infested tree to provide me endless hours of enjoyment. Aphids secrete a sweet, liquid waste product called “honeydew.” This substance attracts an enormous diversity of wasps, bees, flies, and other insects (even butterflies). I found just such a tree, a young aspen, at the Cheyenne Mountain Zoo in Colorado Springs, Colorado last week. Among the numerous hymenopterans seeking refreshment was a mason wasp that goes by the unfortunately long name of Ancistrocerus tuberculocephalus.

Mason wasps are solitary members of the family Vespidae, which includes familiar social species like yellowjackets and paper wasps. Nearly all members of that family fold their wings longitudinally when at rest, so that behavior is often a good way to identify them.

While some of the mason wasps make free-standing nests of mud, the majority nest in pre-existing cavities, partitioning the interior space into separate cells.

Ancistrocerus tuberculocephalus is known to use the abandoned mud nests of the Black and Yellow Mud Dauber, Sceliphron caementarium, for its own nests. It can also dig out the pith in sumac twigs and nest inside the resulting hollow; or it can use old beetle borings in dead wood. The female wasp provisions each cell with paralyzed caterpillars that will be the food source for the single larva that develops in each cell.

This species is divided into two subspecies. A. tuberculocephalus sutterianus ranges from British Columbia to California, Nevada, and Utah. Below is a specimen of this subspecies from near Long Beach, California.

A. tuberculocephalus tuberculocephalus occurs from South Dakota and Wyoming to Utah, Colorado, Arizona, New Mexico, and west Texas. The remaining images in this post are of specimens from Colorado Springs.

You can help provide housing for these flying pest control agents by simply leaving old mud dauber nests where they are. Should you be feeling more industrious, consider bundling old sumac twigs and hanging them under an eave;

or drill six-inch holes of various diameters into a block of wood and tack it up.

Many solitary wasps, and bees, too, need the extra real estate these days as their habitats disappear amid suburban sprawl. The wasps won’t bother you, and you might make some interesting discoveries about them.

Special thanks to David R. Green for use of his image of the twig trap nest, complete with a solitary wasp peering out of it. Thanks also to "Birds n' Such" for the image of the upscale bee block.

Spider Sunday: Wolf Spider

2011-07-24T07:00:00.000-07:00

While living in Massachusetts in 2009 I had the pleasure of prowling around some very nice natural areas with Lynn Harper, an accomplished naturalist who works for the Natural Heritage and Endangered Species Program in the Massachusetts Division of Fisheries and Wildlife. Among the places I went with Lynn was Tully Lake in Royalston. There I was to encounter a very large wolf spider in a wet meadow near the lake.

Scientists have not made it a priority to assign common (English) names to individual species of insects and spiders, unless the creature is of economic significance. Consequently, there is no specific name for this magnificent, eye-catching arachnid. It is probably the species Hogna helluo, though without a thorough physical exam of the specimen it is nearly impossible to be certain. Spiders darken with age, and there is plenty of variability in color and pattern from individual to individual anyway.

Wolf spiders comprise the family Lycosidae, and most of the large North American species belong to the genus Hogna. They used to be classified in the genus Lycosa, but a revision of that genus resulted in the finding that there are no New World species in the genus Lycosa. North American species were thus reassigned to Hogna.

Arachnologists measure spiders by body length, not legspan, but even by that standard, Hogna are real giants. Mature males of H. helluo range from 10-12 mm, while females are a whopping 18-21 mm. Add the sprawling legs and they are an intimidating creature to those unfamiliar with their skittish nature.

Wolf spiders in general hunt “on foot” instead of building webs to snare their prey. Consequently they are more muscular than the average arachnid, with keen eyesight. They are most active at night, perhaps because their arch enemies the spider wasps (family Pompilidae) hunt during the day. Try hunting for wolf spiders yourself, at night. Shine a flashlight or a headlamp over a field, or even a lawn, and you will see the eyes of wolf spiders sparkling like diamonds as they reflect the beam of your light.

Wolf spiders can simply overpower their prey, and if you witness one attacking a cricket or other insect you will probably be shocked by the violence. Still, a wolf spider is going to flee at top speed from your approach. I was fortunate to reel off a number of pictures before this female fled among the grass and moss.

There are many stories to tell about wolf spiders, so I will give away no more secrets today. I will simply encourage you to go out and look for them yourself; and ask that you treat the odd wolf spider that enters your home with a little respect. Please relocate such spiders back outdoors where they can intercept invading insects that could do you, your family and pets real harm. Thank you.

Wasp Wednesday: Not Wasp III

2011-07-20T07:00:00.000-07:00

When it comes to mimicry of wasps, the flower flies of the family Syrphidae are perhaps unequaled. They are convincing enough that I myself remain prone to being fooled by some of these imposters. Among the best of the best are members of the genus Spilomyia, which not only look like yellowjackets, but even sound like them.

A recent trip to Colorado Springs, Colorado revealed just how easy it is to pull the wool over my eyes. At the Cheyenne Mountain Zoo I had been seeing both Aerial Yellowjackets (Dolichovespula arenaria) and Western Yellowjackets (Vespula pensylvanica) licking aphid honeydew off of leaves on a young aspen tree. One of the “yellowjackets” didn’t look quite right, though, and a closer inspection revealed it to be a fly.

One way I am able to tell flower flies from yellowjackets is by the antennae. Yellowjackets have long, thick antennae, whereas most of the flies have very short antennae with a hair-like appendage called an arista on the very tip. Some flower flies, including those in the genus Spilomyia compensate for this difference by waving their front legs in front of their faces to simulate the longer, thicker antennae of the wasps.

Fine. I can always tell the difference by the eyes. Flies have very large eyes that meet at (males) or near (females) the top of their heads. This should be easy. Ok, wait a minute, exactly where do this fly’s eyes end and the rest of its face begin? Swell. The ornate black and yellow markings on the fly’s eyes now make sense: they break up the outline of the eyes, making them appear smaller than they actually are.

Alright, I don’t give up that easily. Flies have only one pair of wings, while wasps have two. Ha! I got you now. Also, the wings of yellowjackets are folded longitudinally when the wasp is at rest, so the wings appear thinner and darker….Uh oh. This fly actually has the front half of each wing darkened to mimic that fold. Unreal.

The flies are also the same size as yellowjackets, varying from 12-17 millimeters in body length. But, as if visual appearance and behavior are not enough to convince a would-be predator not to mess with the fly, this mimic even sounds like a wasp. The frequency of its wingbeats in flight is nearly identical to that of its yellowjacket model. One has to wonder if any predator or parasite can see (and hear) through this charade.

Flower flies are more than just a pretty face, though. The adults visit flowers, and they can be at least adequate pollinators as a result of this behavior. The larval stages of Spilomyia apparently dwell inside water-filled tree holes, feeding on decaying organic matter. So, they are valuable recyclers and decomposers, too.

The next time you think you see a yellowjacket in your yard or garden, do a double-take; maybe a triple-take. You might just be seeing a fly in disguise. Spilomyia is a very widespread genus with about 13 species in North America, so chances are good that they are in your neighborhood.

Spider Sunday: Six-spotted Fishing Spider

2011-07-17T07:00:00.000-07:00

Among my most favorite spiders are the fishing spiders in the genus Dolomedes, family Pisauridae. They are elegant ambush hunters, and perhaps none more so than the Six-spotted Fishing Spider, Dolomedes triton. This species is widespread in North America, but not seen that frequently, being especially scarce in the Midwest and Rocky Mountains.

These are not small spiders, mature females attaining a body length of 17-20 millimeters, and males 9-13 millimeters. Their extensive legspan makes them appear larger still. They can vary considerably in color and pattern from one individual specimen to another, but the “standard” form sports two rows of white spots on the abdomen. They don’t always add up to the spider’s namesake six, though.

Fishing spiders are famed for their feats of predatory strength in killing small fish, tadpoles, and frogs. Indeed, D. triton is capable of preying on aquatic vertebrates four to five times the spider’s own weight. The spider reacts to the concentric waves created by a surfacing organism. The spider cannot see well, but its sense of touch more than makes up for any visual deficiency. It is able to pinpoint the epicenter of waves with extraordinary precision, and strike with lightning speed. Still, it rarely goes after large prey, and succeeds less than 10% of the time (unless the prey item actually bumps into the spider, in which case the success rate increases to 16%). Most items on the spider’s menu are terrestrial or aerial insects that get blown onto the water’s surface, or fall from overhanging vegetation.

D. triton can pursue prey underwater, but that is a rare behavior. It is more likely to dive to avoid its own predators, namely the spider wasp Anoplius depressipes. Fine hairs covering the spider’s body trap a layer of air against its breathing holes when the spider goes under. Again, this is usually a last ditch attempt at escape when all else fails.

The spider normally rests motionless on emergent vegetation or floating objects in the quiet water of a pond, lake, or river backwater, maintaining contact with the water surface with the first two pair of legs. This is not to say that the spider can’t propel itself across the surface of the water if it wants to. It can, in fact, do so passively or actively, and slowly or rapidly.

Fishing spiders can raise their front pair of legs into the wind and be blown by the most imperceptible of breezes. This form of locomotion is called “sailing,” and the spider has little control over its speed. The most common form of movement over the water executed by Dolomedes is called “rowing.” The spider actually makes the water surface itself do the work. The tip of each leg creates a dimple on the water surface, and by stroking the third and second pair of legs backwards (in that order), the dimples act as oars, pushing water toward the rear of the spider and moving it forward. This is a rather leisurely mode and speed of travel.

When a fishing spider wants to flee a predator or pursue fast prey, it can shift to “gallop” speed. In this case, the spider abandons the dimple propulsion strategy and simply slices the water rapidly with the tips of its legs. Its body is elevated above the surface when galloping, and at certain points the animal is completely airborne. This method of locomotion can result in astonishing maximum speeds of three feet per second. The spider cannot sustain that velocity for very long, however.

Male D. triton spiders have the unenviable task of convincing females that they are not an appetizer. So, they may initiate courtship by literally being “jerks,” using their legs to generate an unmistakable series of rhythmic surface waves that contact the female spider. Alternatively, he may follow the female’s silken dragline, then engaging in rapid leg-tapping as he approaches her more closely. The two spiders touch legs in an apparent identity-verification dance.

Mated females create a spherical egg sac that they cart around in their jaws and pedipalps until just before the spiderlings are likely to hatch. At that point the mother spider spins a “nursery web” and suspends the egg sac inside. She will then guard the egg sac, and the spiderlings that hatch from it. Once the spiderlings molt again, they will disperse and the female will resume her normal hunting lifestyle.

Sources: Zimmer, Carl. 2000. “Walking on Water,” Natural History, vol. 109, no. 3, pp 30-31 (April, 2000).

Wasp Wednesday: Therion morio

2011-07-13T07:00:00.000-07:00

Unfortunately, here in the Sonoran Desert of southern Arizona, there is not a great diversity of ichneumon wasps, at least not the larger, more colorful species that one finds routinely in the deciduous forests of eastern North America. I was delighted to find a female specimen of Therion morio at the Vernon Wildlife Area near Mukwonago, Wisconsin on June 25. Even more amazing, it actually paused long enough for me to snap a few images. The one below is the best of the lot in the dim light of the forest understory.

This species is about the size of a black and yellow mud dauber, and it would not be surprising to find it is indeed a mimic of Sceliphron caementarium. The rule of thumb with ichneumon wasps is that if it looks like a stinger, then it isn’t a stinger. Such is the case here. The female has a short, spine-like egg-laying organ called an ovipositor. She does not use it in self-defense, only to inject eggs into caterpillars.

The larvae of this wasp are internal parasites of moth caterpillars, including the Fall Webworm, Hyphantria cunea, so this ichneumon should be considered a beneficial biological control of such pests. Other recorded hosts include the larvae of other tiger moths (family Arctiidae): Cycnia inopinatus; the Virginia Tiger Moth, Spilosoma virginica; the Saltmarsh Caterpillar, Estigmene acrea; and the Spotted Tiger Moth, Lophocampa maculata. While the wasp’s egg is laid in a caterpillar host, the adult offspring will emerge from the moth’s pupal stage.

Therion morio, which has no common English name, is a widespread species ranging from Nova Scotia south to Florida and west to Washington, northwest Nevada, southeast Kansas, and Mexico.

Sources: Carlson, Robert W. 2009. “Ichneumonidae,” DiscoverLife.org

Spider Sunday: Twobanded Antmimic

2011-07-10T07:00:00.000-07:00

You would think that by virtue of the fact that spiders are venomous they have few enemies willing to tangle with them. Such is not the case. Some spiders have therefore evolved to look like other animals that are even more distasteful or hazardous to potential predators. Many spiders resemble ants, for example, and one common example is the Twobanded Antmimic, Castianeira cingulata.

The only reason I was able to get clear images of this particular female specimen was because she had climbed to the top of a doorknob and seemed perplexed as to where to go next. She actually “danced” in place, raising her abdomen and making choreographed movements with her legs. While antmimic spiders in the family Corinnidae are adept hunters, they do not see quite as well as wolf spiders and jumping spiders. I am not sure whether she detected my presence or not, though it seems likely that she did.

At only 7-8 mm in body length for females, and 6-7 mm for males, these are not imposing creatures. Their size does match that of carpenter ants, though, and so does their coloring and overall body shape. The two pale bands on the abdomen may serve to give the impression that there are actually three body segments instead of two. Even more astonishing is that the spiders behave like ants, even appearing in the company of ants to reinforce their disguise. They move reasonably slowly when prowling, bobbing their abdomens and even waving their front legs like a pair of antennae.

Why bother mimicking ants? Carpenter ants in particular are pugnacious creatures that can bite fiercely and also emit formic acid, a very repulsive chemical compound. Few other insects, or spiders and other predators want to take on such an aggressive dynamo, so looking and acting like an ant has its advantages.

Castianeira cingulata ranges from the northeastern U.S. and adjacent southern Canada east to South Dakota and south to Arkansas and Florida. It inhabits woodland habitats, scouring the leaf litter on the forest floor for insect prey. The spiders are active both day and night. The spiders can overwinter in dense silken sacks that they spin in sheltered situations such as rock crevices and the recesses of decaying logs. It is suspected that they can potentially live several years, at least in the southern reaches of their range.

Sources: Kaston, B.J. 1978. How to Know the Spiders (Third Edition). Dubuque, Iowa: Wm. C. Brown Company Publishers. 272 pp.
Gaddy, L.L. 2009. Spiders of the Carolinas. Duluth, Minnesota: Kollath+Stensaas Publishing. 208 pp.
Weber, Larry. 2003. Spiders of the North Woods. Duluth, Minnesota: Kollath+Stensaas Publishing. 205 pp.