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.
Wednesday, January 25, 2012
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.
Sunday, January 22, 2012
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.
Wednesday, January 18, 2012
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.
Sunday, January 15, 2012
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.
Wednesday, January 11, 2012
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.
Sunday, January 8, 2012
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.
Wednesday, January 4, 2012
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.
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.
Sunday, January 1, 2012
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..