Wednesday, December 28, 2011

Wasp Wednesday: Early Mentors

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.

Sunday, December 25, 2011

Spider Sunday: Spider Enemies

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; Acrocerid fly image is of Eulonchus tristis, taken in Washington state by Stephen Hart and borrowed from; Portia spider image taken from sgmacro, by Nicky Bay of Singapore; all other images by Eric R. Eaton unless otherwise noted.

Wednesday, December 21, 2011

Wasp Wednesday: Caliadurgus hyalinatus

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.

Sunday, December 18, 2011

Spider Sunday: Tinus peregrinus

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, 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.

Wednesday, December 14, 2011

Wasp Wednesday: Polistes flavus

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.

Sunday, December 11, 2011

Spider Sunday: Bowl & Doily Spider

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.

Wednesday, December 7, 2011

Wasp Wednesday: Not Wasp V

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”.

Sunday, December 4, 2011

Spider Sunday: Spiders and Celebrities

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.

Wednesday, November 30, 2011

Wasp Wednesday: Gall Wasps

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.

Sunday, November 27, 2011

Spider Sunday: Spider Sex Ed

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.

Mating Neriene sp. dome spiders, Arizona

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.

Epigynum of female Pirata piraticus wolf spider, Massachusetts

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.

Pedipalp of male Bathyphantes sp. sheetweb weaver, Massachusetts

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.

Pedipalp of male Wadotes sp. funnel weaver, Massachusetts

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.

Wednesday, November 23, 2011

Wasp Wednesday: Ant-queen Kidnappers

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.

Sunday, November 20, 2011

Spider Sunday: Coras

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.

Wednesday, November 16, 2011

Wasp Wednesday: Anacrabro ocellatus

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.