Sunday, September 30, 2012

Spider Sunday: "Arachtober" is B-a-a-a-a-a-ck!

Just like the sequel to your favorite horror movie, the Flickr group ”Arachtober” is back tomorrow to feature still more “scary” spider, scorpions, solifuges, and other arachnids.

The group gets bigger and better every year as more people register (free and easy), putting up at least one arachnid image per day. The only requirement of note is that you post images that you have not previously added to your own Flickr photo stream.

I have been saving up all my 2012 spider images for just this occasion, though I have used some of them in this blog. Here’s a preview of what I’ll be adding to Arachtober in the coming weeks:

Ground spider, Zelotes sp. (family Gnaphosidae)

Funnel-web weaver, family Agelenidae

Spinybacked Orbweaver, Gasteracantha cancriformis

Western Lynx Spider, Oxyopes scalaris

Thin-legged wolf spider, Pardosa sp.

Jumping spider, Habronattus sp.

I look forward to seeing your images over there as well. There are enough arachnid experts that contribute that we can probably identify any of your “mystery” spiders as well. Good luck!

Wednesday, September 26, 2012

Wasp Wednesday: Pigeon Tremex Horntail

People who have minimal knowledge of wasps can’t really be faulted for having a startled or panicked reaction when confronted with one of these creatures, especially if it is a large insect. Among the more intimidating of wasps are the horntails in the family Siricidae. They do not sting, but they look like they can. Here in the Front Range of the Rockies, the most common species of Siricidae is the “Pigeon Tremex,” Tremex Columba.

So far, I have encountered only male specimens, resting quietly on foliage at about eye-level. They can be approached easily and closely if you are careful. This is a native species ranging widely from Nova Scotia, New Brunswick and Quebec, south to Florida, and west to Mexico, Arizona, Utah, and Colorado. There are even a few records from southern California.

Siricids in general are more closely related to sawflies than any other wasps. The abdomen is joined broadly to the thorax, giving the entire creature a cigar-shaped appearance. They are about a third the size of a stogie, too. Adult females range from 37-50 millimeters (1.5-2.0 inches). Males average smaller, from 18-37 millimeters. Note that western specimens of Tremex Columba are usually much paler in coloration than eastern specimens.

© Andrew Williams

The females are equipped with what looks like two stingers, one short one protruding from the top of the tip of the abdomen, and another longer, needle-like rod at the bottom of the abdomen. The wasps are, in fact, non-venomous. The top “horn” is called the “cornus,” and both genders possess this spur, which gives the family its common name of “horntails.” I have been unable to find an explanation of the function of the cornus, if there is one. The longer appendage is an egg-laying organ called the “ovipositor.” The female uses this complex part of her anatomy to insert eggs into dead, dying, or weakened hardwood trees. Maple, beech, elm, apple, pear, poplar, oak, hickory, sycamore, and hackberry are all known hosts of this wasp, but other deciduous trees in poor condition are probably utilized as well.

The ovipositor acts like a drill and hypodermic needle. It is housed in a two-part sheath that helps to brace the sawtoothed egg-laying organ as it works its way into bark and wood. Lumberjacks have a vulgar nickname for these wasps, owing to what the wasps appears to be doing when they oviposit into a bole or stump. I’ll leave that epithet to your imagination.

© Andrew Williams

Not only does the wasp lay her eggs in the tree, she also delivers a wood-rotting fungus, Cerrina unicolor to the site of each egg insertion. She stores the fungus in special abdominal glands called mycangia, until she is ready to deploy it. The fungus breaks down cellulose, and both fungus and decayed wood are then consumed by the larval wasp.

Larval horntails are grub-like, and easily mistaken for beetle grubs save for the cornus on the very tip of their worm-like bodies. It usually takes more than one year for the horntail to complete metamorphosis.

© Project Gutenberg (Google)

You would think that a larva tunneling inside a tree or log would be safe from its enemies, but such is not the case. Huge wasps called giant ichneumons can drill down and reach the horntail grubs. One of my most popular blog entries chronicles the life cycle of these Megarhyssa wasps. Yet another kind of wasp attacks younger larval stages of horntails. Wasps in the family Ibaliidae (and genus Ibalia) drill down to reach horntail larvae that are at a more shallow depth.

Female Ibalia sp. © Mark MacMillan/Colorado State University

Pigeon Tremex horntails that survive the perils of youth eventually pupate, emerging as adults most often in late summer or fall. Right now is the ideal time to find them, but you have to look at a lot of dead, standing trees to find them. Horntail species that use coniferous trees as hosts are often attracted to wildfires, since fire often weakens trees. Many wood-boring beetles are also active in the wake of conflagrations.

Please help spread the word that with few exceptions (introduced species like Sirex noctilio for example), horntails are not pests, but merely exploit trees that are already damaged by environmental stress, and/or diseases or other destructive insects. They are important to forest ecology and the average homeowner has no need to control them.

Sources: Cranshaw, Whitney and Boris Kondratieff. 1995. Bagging Big Bugs: How to identify, collect, and display the largest and most colorful insects of the Rocky Mountain region. Golden, CO: Fulcrum Publishing. 324 pp.
Drees, Bastiaan M. and John Jackmann. 1999. A Field Guide to Common Texas Insects. Houston: Gulf Publishing Co. 359 pp.
Evans, Arthur V. 2008. National Wildlife Federation Field Guide to Insects and Spiders of North America. New York: Andrew Stewart Publishing, Inc. 497 pp.
Schiff, Nathan M., Steven A. Valley, James R. LaBonte, and David R. Smith. 2006. Guide to the Siricid Woodwasps of North America Morgantown, WV: USDA Forest Service Forest Health Technology Enterprise Team (FHTET-2006-25). 102 pp.

Sunday, September 23, 2012

Spider Sunday: Another Jumper

Further proof that you do not have to look far for fascinating arachnids: I happened to notice an unfamiliar jumping spider (family Salticidae) prowling across the outside of the French doors on our townhouse last Tuesday, September 18. I took a few pictures, and some of the images turned out to be legible! Seriously, it turned out the spider was a male of Habronattus cuspidatus, not uncommon here in Colorado.

I had to do a bit of searching through to find images that matched my critter, but as luck would have it, males of this species possess a fairly conspicuous character that surprised me. The “knee” joint on the third leg has a very large spur that can be easily seen with a little magnification. Here is an image from Bugguide that illustrates this structure:

©Adrian Thysse

Naturally, I am curious what this spur is used for. Jumping spiders in general are nomadic, hunting “on foot” and using their keen eyesight to spy prey. They also take advantage of their sharp vision when it comes to courtship, males often communicating their identity by signaling with legs and palps. Many male jumpers have the first pair of legs heavily decorated with dense brushes of hairs and/or brightly-colored scales, but those in the genus Habronattus have the third pair of legs modified for visual recognition by females.

Habronattus also uses acoustic signals to complement the visual performance. Males drum or tap, sending vibrations through the substrate (surface on which the animal is standing). Dr. Wayne Maddison rendered this wonderful illustration of a male H. calcaratus, a related species, in its characteristic, crouching courtship posture:

©1979 Agriculture Canada

Notice how the third leg is bent to maximize visibility of that knee joint. Meanwhile, the vibratory signals have been likened to an orchestral composition, so complex are they, and synchronized with visual displays. It is possible that this genus of spiders has the most elaborate courthip of any terrestrial invertebrate (Elias, et al., 2012).

Habronattus is a large genus of small spiders. There are approximately 100 species, most of which occur in North America, the rest in the neotropics. The most diversity is in the southwest U.S., but Florida has many species as well. Still others range above the Arctic Circle and east to coastal Canada. Look for them mostly on the ground in areas of scattered vegetation, where they prowl on stones or amid leaf litter.

Sources: Elias, Damian O., Wayne P. Maddison, Christina Peckmezian, Madeline B. Gerard, and Andrew C. Mason. 2012. “Orchestrating the score: complex multimodal courtship in the Habronattus coecatus group of Habronattus jumping spiders (Araneae: Salticidae),” Biol J Linn Soc 105(3): 522-547.
Maddison, Wayne P. 1995. “Habronattus Version 01,” Tree of Life Web Project

Wednesday, September 19, 2012

Wasp Wednesday: A Tropical Social Wasp

Attention: You. Yes, you. I welcome your images of mystery insects and spiders from anywhere in the world, and will blog the answer to share with others if I have your permission to publish the images. The following is one example of how this might appear.

I often receive inquiries through my private e-mail, asking if I could identify this insect or that spider, sometimes from other corners of the world besides the United States. This is always a welcome challenge, but the emphasis is usually on “challenge.” Not long ago, my friend Paul Kaufman sent me three wonderful images of a social wasp taken by Pablo Yoder, a missionary in Nicaragua. At least I recognized it as something in the family Vespidae, but there is a vast number of genera and species in the neotropics.

© Pablo Yoder

Thanks to Google image searches, I eventually pinpointed the wasp as the species Polybia emaciata. It is one of the few social vespid wasps that builds its nest of mud instead of paper. The more durable nature of the mud envelope allows the wasps to “hunker down” or flee when faced with a potential attack by a vertebrate predator. Contrast this behavior with the violent attacks launched by social wasps that build relatively flimsy nests of paper.

Enclosing a nest helps protect the eggs, larvae, and pupae that inhabit each cell in the horizontal layers of combs made by social wasps. Exposed combs are more vulnerable to predators and parasites since the adult wasps cannot be everywhere at once guarding each member of the brood.

© Pablo Yoder

So what is the wasp in two of these images doing with a big drop of water in its jaws? It is essentially bailing out the nest, keeping the mud from becoming saturated. It rains hard and often in the jungle. Even though the nests of wasps are usually ensconced beneath foliage in the rainforest canopy or understory, a good quantity of water still reaches those nests. The workers begin drinking the water, then walk to the edge of the nest and regurgitate droplets. The thick mud walls of the nests of this species take longer to become saturated than do paper nests of other species, but there is still cause for concern on the part of the nest inhabitants.

Nests of Polybia emaciata are typically inhabited by a small number of adult wasps. Colonies usually number between 100 and 500 wasps, while other species would have a much larger number. The nests vary in size from roughly nine centimeters to 22 centimeters in length, as least in one study in Panama (O’Donnell & Jeanne, 2002). The nests may also persist for several years due to their durability.

© Journal of Insect Science

O’Donnell and Jeanne elicited nest defense responses by tapping on the exterior of the nests, or blowing into the entrance hole. Most wasps would respond by rushing out of the nest and either attacking immediately or adopting an agonistic (warning) posture while perched on the exterior of the nest envelope. Not so with Polybia emaciata, which either flew away (though not abandoning the nest), or took refuge inside. Only sustained, escalated provocation resulted in the wasps exiting the nest, then pummeling and attempting to sting the researchers. Natural predators of tropical social wasps include birds, bats, and monkeys.

© Pablo Yoder

The diversity of wasps in the tropics, their survival strategies, and their relationships to other organisms is fascinating. I hope to one day see some of these remarkable insects for myself, but in the meantime I appreciate my readers sharing their own experiences and images.

Source: O’Donnell, Sean and Robert L. Jeanne. 2002. “The nest as fortress: defensive behavior of Polybia emaciata, a mud-nesting eusocial wasp,” J Insect Sci 2.3. 5 pp.

Sunday, September 16, 2012

Spider Sunday: Labyrinth Spiders

Oh what a tangled web they weave: meet the labyrinth spiders in the genus Metepeira. It may come as a surprise to learn that these little arachnids are in the orb weaver family Araneidae. The first thing one usually sees when spotting their web is the tangled network of lines surrounding a thimble-like retreat decorated with debris. Sometimes the retreat itself is all that is obvious.

There are apparently thirteen species of Metepeira currently recognized as occurring in North America north of Mexico. Only one of these is called the Labyrinth Spider: Metepeira labyrinthea, which ranges in the eastern half of the U.S. and north to southern Ontario, Canada. Look for it in shrubs and the low branches of trees along forest edges. The genus is most diverse in the west and southwest. I have found other species of Metepeira to be reasonably common, or even abundant, in arid habitats in the western U.S. (eastern Oregon and southeast Arizona).

The cobweb-like snare is only half of the structure of a Metepeira web. A small orb web completes the picture, but it is not often easy to see. The spider hides in its tent-like retreat, connected to the hub (center) of the orb web by a signal thread. When a prey insect impacts the orb, the spider dashes down to secure its potential meal.

The spiders themselves are not very large. Mature females are 5.5-7.2 millimeters in body length, while males measure only 3-4.5 millimeters. Because their color pattern is so variable, labyrinth spiders can be easily confused with other kinds of orb weavers. This is especially true if you find a specimen that has no associated web. Mature males wander in search of females, so they are often encountered on vegetation without a web.

These spiders usually reach adulthood in late summer or early autumn, at least in more northerly latitudes. Mated females create one or more egg sacs, each of which is roughly cone-shaped and covered in brown, papery silk. The spider stacks these above her in her web.

Interestingly, the species Metepeira spinipes, which ranges from southern Oregon into Mexico, sometimes exhibits social tendencies, individual spiders interlacing their webs over large areas. This cooperative behavior tends to be associated with higher-than-normal prey availability, and also certain kinds of habitats. Prey abundance in turn coincides with years in which the El NiƱo weather phenomenon asserts itself.

The social nature of that species and the Mexican Metepeira incrassata has another benefit: it reduces the likelihood of any one female spider will be killed by a spider wasp (Pompilidae: Poecilopompilus mixtus); or have her egg sacs fall prey to parasitic wasps (Ichneumonidae).

Sociality is not without its costs, however, and Metepeira incrassata colonies are often infiltrated by kleptoparasitic spiders akin to the ”dewdrop spiders: I wrote about last year. Other kleptoparasitic spiders actually kill the labyrinth spiders outright.

Enjoy looking for labyrinth spiders right now, as this is the time of year they are most in evidence. Just don’t become entangled in trying to identify them to species.

Sources: Balaban, John and Jane, et al. 2012. “Genus Metepeira,”
Hieber, Craig S. and George W. Uetz. 1990. “Colony size and parasitoid load in two species of colonial Metepeira spiders from Mexico (Araneae: Araneidae),” Oecologia 82(2): 145-150.
Kaston, B. J. 1978. How to Know the Spiders (Third Ed.). Dubuque, Iowa: Wm. C. Brown Company Publishers. 272 pp.
McCrate, Andrea T. and George W. Uetz. 2010. “Kleptoparasites: A two-fold cost of group living for the colonial spider, Metepira incrassata (Araneae: Araneidae),” Behav Ecol Sociobiol 64(3): 389-399.
Rayor, Linda S. 1996. “Attack strategies of predatory wasps (Hymenoptera: Pompilidae; Sphecidae) on colonial orb web-building spiders (Araneidae: Metepeira incrassata),” J Kans Entomol Soc 69(4): 67-75.
Uetz, George W. and Wesley Burgess. 1979. “Habitat structure and colonial behavior in Metepeira spinipes (Araneae: Araneidae), an orb weaving spider from Mexico,” Psyche 86: 79-90.

Wednesday, September 12, 2012

Wasp Wednesday: Dasymutilla bioculata

Last Sunday I wrote about a brightly-colored jumping spider, Phidippus apacheanus, and suggested that it was probably a mimic of wingless female wasps called velvet ants. Today I would like to introduce you to one of those wasps. Velvet ants comprise the family Mutillidae, and can be found across most of the North American continent. They are most common in arid habitats like deserts and prairies. Here in Colorado Springs, Dasymutilla bioculata is one of the most frequently encountered species.

Many velvet ants are bright orange, red, or yellow, and black. This pattern advertises the fact that females can sting. So powerful is that sting that one of the larger species is called the “cow killer.” Folklore has it that the pain is enough to kill livestock. It is no mystery why less well-defended insects, or spiders, would want to look like velvet ants. No sensible predator wants to mess with them.

I have seen female Dasymutilla bioculata scurrying over sandy paths in open fields, usually on overcast days or around dusk when the air temperature begins to cool slightly. Both genders like to clamber around on the stems and leaves of Common Sunflower, Helianthus annuus. They find the sweet, sticky secretions of the plant to their liking.

Male velvet ants have the customary two pairs of wings and fly well, but they can also be colored very differently from their female counterparts. This has resulted in much confusion, even among experts who seek to associate the males with the appropriate females and vice versa.

Dasymutilla bioculata is an excellent example of “lumping,” whereby scientists decide that several different species are actually variations of just one species. A paper published in 2010 resulted in lumping no fewer than twenty-one former species and subspecies under the name Dasymutilla bioculata. The authors of the publication used molecular analysis to find common nuclear ribosomal RNA markers among all the former species and subspecies. Morphological differences (what you see when you look at the external structure of the insects) were deemed too inconsistent to be the sole determining factors in differentiating species.

No wonder I didn’t recognize these Colorado specimens. George Waldren, a velvet ant expert and volunteer editor at was kind enough to set me straight, identifying my images of the females. The images of the male shown here may or may not be the same species. You just can’t tell from images alone.

Dasymutilla bioculata ranges across the entire continent, and from southern Canada to Mexico. Adults vary in size from about 8 millimeters to 16 or 17 millimeters in body length. The bigger the specimen, the better it fed as a larva.

The life histories of velvet ants are often as mysterious as their classification, or simply unknown. Those species we do know well are parasitic on other insects, especially other solitary wasps and bees. Female velvet ants scour the ground for signs of their hosts, which often dig burrows in the soil. Velvet ants can even detect closed burrows, digging them open to gain access. Once inside, the female lays an egg in the cell or cells at the end of the underground tunnel. The larval wasp that hatches will attack the pupa of the host, or a larva in diapause (inactive state).

The known hosts for Dasymutilla bioculata are sand wasps in the genera Bembix and Microbembex. Should an adult sand wasp discover a velvet ant invading her nest, she will of course attack it. Velvet ants have an extra-thick exoskeleton that effectively deflects the bites and stings of their enemies.

I would advise anyone searching for velvet ants to avoid picking them up. Do scoop one into a vial some time and put it up to your ear. Do you hear that? Both genders of these wasps can “squeak” by rapidly rubbing their abdominal segments together. Music to my own ears anyway.

Sources: Kits, Joel, et al. 2011. “Species Dasymutilla bioculata,”
Krombein, Karl V. and Paul D. Hurd. 1979. Catalog of Hymenoptera in America North of Mexico. Washington, DC: Smithsonian Institution Press. 2188 pp.
Williams, K.A., D.G. Manley, E.M. Pilgrim, C.D. von Dohlen & J.P. Pitts. 2010. “Multifaceted assessment of species validity in the Dasymutilla bioculata species group (Hymenoptera: Mutillidae). Syst Entomol, 36(1): 180-191.

Tuesday, September 11, 2012

Why I do not endorse entomophagy

It has lately become quite fashionable among entomologists to promote entomophagy, the practice of human consumption of insects as food. This is nothing new in Asia, and among many populations in the rural tropics, but is a novel concept among Westernized cultures. I personally know several entomologists who are at the forefront of the “bug chef” phenomenon. They are genuinely nice people, but I am not on board with the idea for a variety of reasons:

1. Fear Factor. Do you remember this television show from NBC? Eating insects, or spiders or other arachnids, was a grotesque challenge to contestants on this “reality” program. Throughout the developed world, eating insects is seen as something starving prisoners do, or people lost in the wilderness without other recourse. It is a punishment or last resort, not a decision one makes when they have other choices. There is good reason for that. Many insects taste horrible, or are downright poisonous if ingested. Mushrooms are a good comparison, except I think they actually taste just fine. There is no question that those pushing bug-eating have an uphill climb in overcoming the “yuck factor.”

2. Nutritional Value. Insects are basically fat and a little protein encased in chitin (the exoskeleton). Proponents of entomophagy will claim there is more to it than that, but I am boiling it down (microwaving it, whatever) to the most simplistic terms. I will not argue that as a supplement to a largely vegetarian diet, eating insects has merit. Still, the chitin, while perhaps pleasingly crunchy, is most reminiscent of those translucent yellow flakes from popcorn that you are still trying to get out from between your teeth days or weeks later. I say this as someone who has personally tried fried mealworms and other “delicacies.”

3. The utilitarian view. What I find truly objectionable about the promotion of entomophagy is the idea that insects must have some anthropocentric, utilitarian use to be of any value. They must also be dead to have value. The living insect is by far more fascinating and important than a dead one with a toothpick through it. Insects pollinate wildflowers and crops. Insects quickly consume dead and decaying flora and fauna before the corpses can breed horrible disease-causing bacteria. Insects are consumed by other animals that we find far more tasty, like fish and poultry for example. Ok, I’m kidding a little bit, but insects are an incredibly important part of the natural food chain.

Insects also produce goods and services that are of great use to humanity. Would we suddenly see the honeybee as food itself, instead of as a maker of food? I know a professor who has had contracts with the Department of Defense to study the employment of insects as detectors of explosives and other substances used by terrorists. This kind of work actually enhances our admiration of insects and their superior chemo-tactile senses. Other scientists study insects to find ways of improving the aerodynamics and mechanics of flying aircraft; and as models of locomotion for robotics. Insects are not products, but that is the only context in which some people think they have value.

I will always hold my fellow entomology colleagues in high esteem, but I do wish they would step off the entomophagy bandwagon for a spell and talk to the public more about the intrinsic value of beetles, wasps, bugs, and flies. Meanwhile, I suspect the comments on this post to offer plenty more “food for thought.”

Sunday, September 9, 2012

Spider Sunday: Apache Jumping Spider

Jumping spiders in the family Salticidae are arguably the most colorful of all spiders, often quite conspicuous despite the fact they are usually rather small in size. Here in North America, the genus Phidippus includes some of our largest jumpers. I have found one bright species to be quite common in recent weeks here in Colorado Springs. Phidippus apacheanus is the Apache Jumping Spider, if I can assume it has that common name.

Just yesterday, September 8, I found two specimens on two separate sunflower plants. They appeared to be basking, but more likely they were waiting for potential prey to come within pouncing range. The male, black on the bottom and legs and bright orange on top, may mimic the velvet ants that also frequent sunflowers. Females have a dark dorsal stripe that runs up the middle of the abdomen.

These are not the largest of our jumping spiders, but still bigger than most salticids. Males range from 5.2-10.6 mm, while females measure 7.1-13.3 millimeters. At least one of the specimens shown here may also be immature, one molt or so away from adulthood. Mature individuals can be found at almost any time of year, though males in particular are most common in autumn.

Despite the western-sounding name, this species ranges over most of the United States save New England and the Pacific coast states. Most records do come from the southern half of the U.S. and into Mexico and Cuba.

The habitat preferences for the Apache Jumper may also explain its abundance in certain regions. It is most often found in grasslands, prairies, plains, and dry fields, up to 6,000 feet or so in elevation. Look for it on shrubs, perennials, cacti, and yucca where it prowls for insect prey. Even wasps can fall victim, like the little crabronid captured by this male on August 27.

Females of Phidippus apacheanus fashion egg sacs in protected niches, such as beneath the bark on oak logs. There they guard the sac and the spiderlings that emerge from it.

This species occurs in areas where other, similar species of Phidippus can also be found, so you can’t always rely on color pattern alone to identify it. The only way to confirm which species a given specimen belongs to is to put it under a microscope and examine its external genitalia. You still might not be able to reach a conclusion if the specimen is immature.

While I am always curious as to exactly what I am taking an image of, I can still delight in the colorful nature and vibrant personalities of jumping spiders. Their alertness is engaging (if not maddening when they dodge to the other side of a stem), and suggests a level of awareness and intelligence that most other arthropods do not possess. Happy spider hunting.

Source: Edwards, G.B. 2004. “Revision of the Jumping Spiders of the Genus Phidippus (Araneae: Salticidae),” Occasional Papers of the Florida State Collection of Arthropods vol. 11. 156 pp. (available for sale here).

Wednesday, September 5, 2012

Wasp Wednesday: Perilampid Wasps

Do you remember that old saying that “good things come in small packages?” That is certainly the case with the compact little wasps known as perilampids (family Perilampidae). They range in size from 1.3-5.5 millimeters in length, but oh are they spectacular. Many, if not most, are brilliant metallic green or blue. Some are wholly black in color. They can be easily confused with small cuckoo wasps in the family Chrysididae, and are sometimes found in similar situations, especially around aphid colonies, or the extrafloral nectaries of sunflowers.

My latest encounter with a perilampid was indeed on a sunflower plant, where it was intent on imbibing the sweet excretions from the hairy stem. I recognized it as a perilampid by the short, strongly elbowed antennae, and the abdomen, which in perilampids is shaped more or less like a triangle or an inverted pyramid. Cuckoo wasps have an oval or rounded abdomen without sharp corners.

The beauty of these tiny insects is more than matched by their bizarre lifestyle. They are parasitic in the larval stage, usually on other parasitic insects like the larvae of tachinid flies, or ichneumon wasps or braconid wasps living as parasites inside caterpillars or other insect larvae. This is known as “hyperparasitism,” whereby they are parasites of parasites.

Even stranger is the way the wasps find their hosts. The female perilampid “broadcasts” large numbers of eggs, laying them on leaves, buds, cracks in bark, under lichens, and in other locations where the larvae that hatch might have hope of encountering a host. She may deposit as many as 500 eggs in this manner. A flattened, mobile larva (“planidium” or “planidiform”as scientists call it) hatches from each egg, and attempts to attach itself to any moving object by its mandibles. Obviously, a great many such planidium larvae fail because they glom onto the wrong animal.

Those that are successful in finding the appropriate secondary larval host then penetrate the host’s cuticle. Once inside they begin searching for the primary host, a parasite of the secondary host. They will then enter that larva in the same way. There they wait until this primary host pupates. The perilampid larva then exits, molting into a grub-like larva that feeds as an external parasite. It goes through two or three more instars (the intervals between molts) before pupating itself inside the host cocoon or puparium.

Some perilampids in the subfamily Perilampniae are able to adjust their life cycle in the absence of a primary host, simply feeding as a parasite on the secondary host. Perilampus hyalinus is such an example, able to complete its life cycle as a parasite of certain sawfly larvae (Diprionidae, Tenthredinidae) if no primary host is contained within it. Another species of Perilampus is recorded from immature grasshoppers (Acrididae), gaining access via flesh fly parasites (Sarcophagidae). Still other species in the subfamily are recorded as primary parasites of lacewing larvae (Chrysopidae), wasp larvae (Sphecidae), and beetle larvae (weevils in the Curculionidae).

The life cycles of members of the subfamily Chrysolampinae are less well known, but records indicate beetle larvae (Lycidae, Anobiidae, Nitidulidae) as hosts.

The classification of perilampids has given scientists fits. They are variously set aside as their own family (Perilampidae), or lumped in with the Pteromalidae. Even if ascribed to their own family, those members of the subfamily Chrysolampinae are usually put into the Pteromalidae. I don’t get it either. The number of recognized genera is also up for discussion. Some authorities recognize only fifteen genera in the world, whereas others suggest there may be as many as twice that number (thirty genera). There are 260-277 species currently recognized, with 36 species in North America north of Mexico (in five genera). Many more species await discovery and/or names and descriptions.

Sources: Goulet, Henri and John T. Huber (eds.). 1993. Hymenoptera of the World: An identification guide to families. Ottawa, Ontario: Agriculture Canada. 668 pp.
Pitkin, B.R. 2004. “Perilampidae,” Universal Chalcidoidea Database, Natural History Museum, United Kingdom
Grissell, E. Eric and M. E. Schauff. 2003. “Family Perilampidae,” Systematic Entomology Laboratory, USDA Agrigultural Research Station, Beltsville, Maryland.
Grissell, Eric. 2010. Bees, Wasps, and Ants: The indispensable role of Hymenoptera in gardens. Portland, Oregon: Timber Press. 335 pp.

Sunday, September 2, 2012

Spider Sunday: No Spider :-(

Sorry, folks. Family is in town from out of state for this Labor Day weekend, and I didn't find time to create the usual post. "Spider Sunday" will return next week at its regularly-scheduled time. Thank you for understanding.