Thursday, August 28, 2014

White-whiskered Grasshopper

One of the most abundant, yet inconspicuous grasshoppers in North America is the little White-whiskered Grasshopper, Ageneotettix deorum. Easily overlooked as just another drab grasshopper, it can be easily recognized by its white antennae and red or orange hind tibia ("shin" segment on the hind leg).

This species is a member of the family Acrididae and the subfamily Gomphocerinae, known as slant-faced grasshoppers. The head of the White-whiskered Grasshopper is not as acutely sloped as its relatives, but it shares other subtle characters in common.

While most slant-faced grasshoppers are found clinging to grasses in the vertical plane, A. deorum is perhaps most often seen on the ground. When flushed from its hiding place it may leap into the middle of a trail where it could either hunker down, hop away again, or crawl rapidly into nearby grass tussocks. Only when it is walking do you easily see those bright red hind legs.

This is not a particularly large grasshopper, males ranging from 11-28 millimeters, female 15-28 millimeters. It is one of the few species in which both genders are nearly identical in size.

The White-whiskered Grasshopper occurs from the Great Lakes (Michigan, south and west to Indiana, Minnesota, and Illinois) through most of Missouri, western Arkansas, and Texas, all the way to the Pacific coast (southeast British Columbia, eastern Washington and Oregon, and much of California). Adult specimens can be found commonly from mid-July through early October.

Ageneotettix deorum frequents dry grasslands with short grasses, so I find it abundantly here in Colorado Springs on the fringe of the Great Plains. I still get confused periodically because of the variability of this species in terms of size and markings. Larger individuals can certainly be mistaken for grasshoppers of other genera. Other grasshoppers can have white antennae, and the White-whiskered Grasshopper can occasionally have darker antennae. The hind tibia is usually hidden under the edge of the hind femur when the insect is at rest, and there are simply few other consistent markings to go by.

The sheer abundance of this species puts it in the category of a rangeland and crop pest. During outbreaks there can be up to 25 adult specimens per square yard; and the species can account for fifty percent or more of the grasshopper fauna. Wheat is particularly vulnerable, but A. deorum also enjoys Kentucky Bluegrass and other kinds of music...I mean....forage. It will even feed on dried, fallen grassblades, seeds, dung, and deceased insects.

Eggs are laid in the soil in the summer and fall, hatching the following spring. Nymphs progress through five instars before reaching adulthood, roughly 40-48 days after emerging from the egg. The adults fly well, but flights are generally short (3-6 feet), and mere inches over the ground.

Sources: Bland, Roger G. 2003. The Orthoptera of Michigan. East Lansing: Michigan State University Extension Bulletin E-2815. 220 pp.
Capinera, John, L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca, New York: Comstock Publishing Associates (Cornell University Press). 249 pp.
Helfer, Jacques R. 1972. How to Know the Grasshoppers, Cockroaches, and Their Allies. Dubuque, Iowa: Wm. C. Brown Company Publishers. 359 pp.
Pfadt, Robert E. 1996. "Whitewhiskered Grasshopper," Wyoming Agricultural Experiment Station Bulletin 912

Tuesday, August 26, 2014

Scolops Planthoppers

Some insects are so unique that they cannot be mistaken for anything else. The planthoppers in the genus Scolops, family Dictyopharidae, are cute, squat little insects with an elongated "nose." Think of the caricature of Cyrano de Bergerac, shrunk down to about 5-8 millimeters.

a specimen from Colorado

There are currently 32 recognized species of Scolops, and the genus is unique to southern Canada, the U.S., and northern Mexico. Though they feed on plant sap, they are not pests of any crop, so consequently very little is known about their biology. They all look pretty much alike, being straw-colored, brown, or gray with the characteristic horn.

a specimen from Iowa

Some species have short-winged forms in addition to the usual long-winged form. Differences in the venation of the front wings have been used in separating the species. The number, length, and arrangement of spines at the tip of the hind tibia ("shin" segment) has also been a character used to differentiate similar species.

The fourth-instar nymphs of at least some Scolops species produce wax from glands near the rear margin of some of the abdominal segments. Most planthoppers in the superfamily Fulgoroidea produce waxy secretions that help repel predators, or disguise the 'hopper as cottony plant debris.

a specimen from Arizona

In my own experience, Scolops are most common in arid habitats, especially dry fields, prairies, and grasslands, even in otherwise moist climates. There are a few host plant records for these planthoppers, compiled on the University of Delaware website cited below. Most host plants seem to be in the families Asteraceae and Chenopodiaceae.

I call Scolops "rhinoceros planthoppers," but there appears to be no formal common name for the genus. One species, S. perdix, is known as the "Partridge Scolops." They certainly can "hop," and this habit may make it difficult to know whether a given specimen is feeding on a particular plant, or simply landed there after hopping to escape your approach.

another Colorado specimen

Sources: Bartlett, C.R. 2014. "Genus Scolops Schaum, 1850," Planthoppers of North America. College of Agriculture & Natural Resources, University of Delaware.
Lawson, Paul B. and R.H. Beamer. 1930. "Some New Scolops (Homoptera, Fulgoridae) with Notes on Other Species," J. Kans. Entomol. Soc. 3(3): 67-72.
Liang, Ai-Ping and Michael R. Wilson. 2002. "Wax-secreting, Cuticular Structures in Nymphs of Scolops abnormis Ball (Hemiptera: Fulgoromorpha: Dictyopharidae)," J. Kans. Entomol. Soc. 75(2): 132-137.
Osborn, Herbert. 1938. "The Fulgoridae of Ohio," Ohio Biol. Survey Bull. 35, 6(6): 283-357.

Friday, August 22, 2014

Colorado's State Insect: Colorado Hairstreak Butterfly

You can't say that the Colorado state legislature has never done anything good. Back in 1996 it passed a bill making the Colorado Hairstreak, Hypaurotis crysalus, the state insect. Heidi and I finally got to see this magnificent butterfly this past Monday, August 18, in North Cheyenne Cañon Park here in Colorado Springs, after looking in vain for the last 3-5 years.

Just why this insect is so elusive is something of a mystery to me, though we noticed that the butterflies favored healthy oak trees free of most galls and other signs of weakness. The Gambel's Oak, Quercus gambeli, is the host plant for the larva. The oak is widespread at elevations from about 6,500 ft. to 7,500 ft., so the butterflies should be equally abundant one would think.

These are fairly large butterflies for members of the hairstreak family Lycaenidae, with a wingspan of 32-38 millimeters. They normally rest with wings closed, and their dull gray underside, striped with white and brown lines, a little orange and blue trim, make it easy to overlook them. When they open their wings to bask, however, they reveal their full glory. The dorsal surface of the wings is largely vivid purple, with black margins and a black patch or band on the forewing. Bright orange spots along the edges, and delicate "tails" on the hind wings add some pizzazz.

Males, like most hairstreaks, are territorial and will defend a given oak tree from rivals. We witnessed several instances of one male chasing another on a south-facing slope in the park at an elevation of slightly more than 7,000 ft.

This species rarely, if ever, visits flowers for nectar. Instead, it feeds on fermenting sap from wounds in trees, on the exudates of developing acorns (see image above), and on the honeydew secreted as a waste product by aphids and scale insects.

The larval stage of the butterfly is yellowish green, slug-like in form, and exceedingly cryptic. We may want to go looking for that stage next spring to complement our images of the adults. In late summer and fall, the female butterflies lay their eggs individually on branches and twigs of the host tree, where they overwinter. The caterpillars that hatch then consume the new oak foliage as it develops.

The story of the rise of this butterfly to the status of State Insect involves the usual lobbyists: School children. In this case, it was thanks mostly to the fourth grade class of teacher Melinda Terry at Wheeling Elementary in Aurora, Colorado.

There is but one generation of this butterfly annually, and while specimens have been recorded from May to November, they reach peak abundance in July and August. Besides Colorado, this insect is found in Utah, Arizona, New Mexico, the southeast edge of Wyoming, and extreme eastern edge of Nevada, barely inching across the border.

The "type" specimen, from which the species was described, was collected at Palmer Lake in El Paso County, Colorado (just north of Colorado Springs), in 1873. At least, that was the year of publication of the description, by W.H. Edwards.

Look for the butterflies to be active even on cloudy days, and right up until dark. Indeed, we encountered them after a thunderstorm skirted the Seven Bridges Trail in the park, on our way back to our car.

Sources: Brock, Jim P. and Kenn Kaufman. 2003. Kaufman Field Guide to Butterflies of North America. Boston: Houghton Mifflin Company. 384 pp.
Cranshaw, Whitney and Boris Kondratieff. 2006. Guide to Colorado Insects. Englewood, Colorado: Westcliffe Publishers. 232 pp.
Ferris, Clifford D. and F. Martin Brown. 1981. Butterflies of the Rocky Mountain States. Norman: University of Oklahoma Press. 442 pp.
Lotts, Kelly and Thomas Naberhaus. 2014. "Colorado Hairstreak," Butterflies and Moths of North America (BAMONA).

Wednesday, August 20, 2014

Aphid Killers: Pemphredon Wasps

Aphids are the insect equivalent of the wildebeest: they exist in vast numbers, and pretty much everything else eats them. Some other insects even specialize on aphids as prey. Chief among those are the "aphid wasps" in the genus Pemphredon, family Crabronidae (formerly a part of the family Sphecidae).

Not surprisingly, aphid wasps are not very large. Most are only ten millimeters in length if not smaller. They are solid black, and look a bit like a miniature thread-waisted wasp, the abdomen being on a short stalk (petiole) attached to the thorax. They have a cubical (square) head. These wasps are forever on the move, so it is very difficult to observe them, let alone get images.

The genus Pemphredon includes 20 recognized species in North America north of Mexico. Collectively, they range over most of the continent.

© Judy Jay in Bohart & Menke, 1976

Aphids are most abundant in spring and fall, so it is no surprise that Pemphredon are most commonly seen in May, then again in August and September. Pay attention to any aphid colony on a tree or weed, and eventually you will see these little wasps hunting. It is likely they also feed on aphids as adult wasps. Aphid wasps will visit flowers, but are only occasionally seen on blossoms.

Pemphredon are solitary wasps, each female making her own nest. She uses pre-existing cavities in wood, hollow stems, or she tunnels through the pith of broken twigs or berry canes. In fact, stems with thorns may be preferred because they are not likelyto be consumed by vertebrate herbivores.

I once spotted an uncharacteristically motionless Pemphredon on the side of a log. It was unmoved as I took images, until....a female made a hurried exit from a tunnel. Both wasps landed so close to me that I managed only one half-focused image of the pair, male on top, before they split. He had been waiting just outside her nest tunnel in hopes of mating with her. You can see her two antennae protruding from her hole, just in front of the male wasp in the above image.

The female wasp hunts aphids in their colonies, plucking them off stems and leaves with her jaws, stinging them into paralysis or simply crushing them, and then flying them back to her nest. She will stockpile ten to several dozen victims. One industrious female Pemphredon lethifer in England harvested 89 aphids for one cell! She will lay an egg after the last victim is gathered, but the egg may be placed at the back of the cell or halfway to the front.

Once she completes a cell, she then creates a partition, usually of chewed plant pith or sawdust, to close the cell, and create the bottom of the next cell. These partitions can be very thick, over 25 millimeters in some cases, perhaps the better to discourage parasites from digging through. She thus fills the tunnel from bottom to top, with as many cells as it will acoomodate. In situations where a twig is wide enough, some Pemphredon species will create branching tunnels instead of a single linear one.

Sometimes, the female wasp will guard the front of her completed nest to chase off potential parasites or competitors. Small carpenter bees (Ceratina spp.), compete for the same pithy-twig nesting sites as Pemphredon, and are not above destroying the wasp's nest to create their own living space.

Tiny cuckoo wasps (Omalus spp.) are parasites of Pemphredon nests, as are ichneumon wasps (Perithous mediator), bee flies (Anthrax irroratus), satellite flies (Senotainia trilineata), and other wasps and flies.

You can create housing for aphid wasps simply by drilling small diameter holes in a block of wood and hanging it off the ground under a protected place, like the eave of a garden shed. There are also ready-made lodges sold commercially for solitary bees that can be modified to suit the wasps, too.

Sources: Bohart, R.M. and A.S. Menke. 1976. Sphecid Wasps of the World. Berkeley: University of California Press. 695 pp.
Dollfuss, H. 1995. "A World Revision of Pemphredon Latrielle 1796 (Hymenoptera, Sphecidae)," Linzer biol. Beitr. 27(2): 905-1019.
O'Neill, Keven M. 2001. Solitary Wasps: Behavior and Natural History. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 406 pp.

Monday, August 18, 2014

Wasp Mantisfly

Maybe I am simply excitable in general, but I was ecstatic to find a truly astonishing insect species earlier this week here in Colorado Springs. I spied what I thought was an ordinary paper wasp (Polistes sp.) on the underside of a sunflower blossom, but something wasn't quite right. Short, quivering antennae finally betrayed it as the Wasp Mantisfly, Climaciella brunnea. These bizarre insects are most closely related to antlions and lacewings in the order Neuroptera.

As I wrote in the Kaufman Field Guide to Insects of North America, mantispids "resemble a science experiment gone horribly wrong. Imagine shrinking a praying mantis, then attaching its front end to the hind end of a lacewing, and you have a mantispid."

In the case of C. brunnea, the body form has been further modified to look like a paper wasp. The resemblance is uncanny. The base of the abdomen is constricted into a "wasp waist," and the wings are rotated such that they fold over the back instead of pitched roof-like as in other mantispids. Even more amazing, the leading half of each wing is darkened, to resemble the longitudinal fold in the wings of vespid wasps. When startled, the Wasp Mantispid even splays its wings like an agitated paper wasp.

Wasp Mantisfly in defensive pose

An actual paper wasp, Mischocyttarus flavitarsis

As if the adult insect is not strange enough, the life cycle is simply mind-boggling. The adult female C. brunnea deposits clutches of literally hundreds, even thousands of eggs, each on a short filament, usually on the underside of leaves. The tiny larvae that emerge probably drop to the ground. They then adopt a posture whereby they are standing more or less upright, on their hind end, swaying, and legs waving in the air. They aim to glom onto passing spiders. Only one larva per spider will survive, and competition must be keen. Assuming only one larva boards a given spider in our example, the story progresses this way: The larva clings to the margin of the spider's carapace (top part of the cephalothorax), waiting for the spider to reproduce. Should the spider be a male, the larva must transfer to a female during mating. The mantispid larva must then wait until the female begins constructing an egg sac.

Before the female spider finishes closing her egg sac, the mantispid larva must enter the sac. The larva cannot penetrate an egg sac that is completely enclosed in silk. Once inside, the larva begins feeding on the spider eggs.

At least three wolf spider hosts have been recorded for C. brunnea: the Rabid Wolf Spider, Rabidosa rabida, and two unidentified members of the genus Schizocosa (Redborg and Redborg, 2000) in Illinois. The entire life cycle from egg to adult requires at least one year.

Look for the adult mantispids on flowers, especially sunflowers, thistles, and milkweed, where they wait to ambush other insects. I found a total of five specimens in quick succession on sunflowers at the edge of a big vacant field of shortgrass prairie on August 13, 2014, and three more on August 15 in the same location. So, they can be very localized in abundance.

Apparently the males live but a very short time, less than a week. Females persist for about a month. Emergence times vary, between May and October, but the overwhelming majority seem to be seen in June, July, and August.

This species is widely distributed, and while considered scarce is probably more common than we realize. It is recorded from southern Canada and nearly every state except the Pacific coast states, Idaho, and Nevada, then south through most of Central America.

Sources: Boyden, Thomas C. 1983. "Mimicry, Predation, and Potential Pollination by the Mantispid Climaciella brunnea var. instabilis (Say) (Neuroptera: Mantispidae)," J. NY Entomol. Soc. 91(4): 508-511.
LaSalle, Mark W. 1986. "Note on the Mantispid Climaciella brunnea (Neuroptera: Mantispidae) in a Coastal Marsh Habitat," Entomol. News 97: 7-10.
Leckie, Seabrooke. 2010. "Mantisfly," The Marvelous in Nature.
Redborg, Kurt E. and Ellis G. Macleod. 1983. "Climaciella brunnea (Neuroptera: Mantispidae): a mantispid that obligately boards spiders," J. Nat. Hist. 17(1): 63-73.
Redborg, Kurt E. and Annemarie H. 2000. "Resource Partitioning of Spider Hosts (Arachnida, Araneae) by Two Mantispid Species (Neuroptera, Mantispidae) in an Illinois Woodland," J. Arachnol. 28(1): 70-78.

Thursday, August 14, 2014

The Homesteader (Plains Lubber grasshopper)

There are not that many insects that you can spot from your car driving at high speed, but the Plains Lubber, Brachystola magna, might be one of them. This heavyweight is a fixture of the Great Plains from the Canadian border to central Mexico. Adult females measure 5-6 centimeters (or more, depending on which resource you consult), while males are a mere 4 centimeters, but they are among the bulkiest of North American insects.

According to one source (Pfadt, 1996), female Plains Lubbers average 4,287 milligrams (0.15 ounces); adult males average 3,935 milligrams (about 0.14 ounces). This might not sound like much, but it is spectacularly weighty compared to your average insect.

The sheer size of Brachystola magna is enough to attract your attention, but they are pretty colorful, too. Most specimens tend toward brown, tan, or beige with black speckling and often a blush of red. Other specimens, especially females, can be bright green. Still others are pink or even blue. These grasshoppers become somewhat duller in color as they age.

The life cycle of the Plains Lubber, also known as the "Homesteader," begins when a female deposits gourd-shaped egg pods in the soil during summer and early fall. Each pod contains 20-35 eggs. The eggs overwinter and are able to remain viable for years during unfavorable conditions such as droughts. Nymphs begin emerging from the eggs in May or June over much of the species' range, though monsoon rains trigger hatching in the southwest U.S.

Nymphs pass through five instars (an instar being the interval between molts) before reaching adulthood. This takes roughly 45 days, during which time the insects are feeding mostly on the foliage of sunflowers and other broadleaf weeds like hoary vervain, annual sowthistle, even dandelion.

Nymph, from Arizona

Adult Plains Lubbers do not confine themselves to a vegetarian diet. Females especially will happily scavenge on their road-killed kin, or devour weak or injured insects, and may even capture and consume smaller grasshoppers. Most members of the order Orthoptera are likewise omnivorous, to one degree or another.

The Plains Lubber can be abundant enough to be a pest, but because it is flightless, the wings reduced to mere pads behind the thorax, its ability to disperse is limited. Just the same, they are powerful leapers, females under distress jumping over one foot, and males up to nine feet when...."encouraged." Normally, a "hop" amounts to 3-5 inches.

Look for these insect giants in marginal habitats such as roadsides, the edges of field crops, and disturbed rangeland. They also occupy shortgrass and tallgrass prairies, desert grasslands, sandhills, and any place with abundant sunflower. Adult specimens can be found as early as mid-June, but they are more abundant in July and August, persisting well into the fall, even November.

Lubbers are often classified in their own family, Romaleidae, or the subfamily Romaleinae under the family Acrididae. There are a total of seven genera and nine species of lubbers in the U.S. All are robust, flightless insects.

Sources: Capinera, John L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 249 pp.
Pfadt, Robert E. 1996. "Plains Lubber Grasshopper," Wyoming Agricultural Experiment Station Bulletin 912

Tuesday, August 12, 2014

Harlequin Bug

It is a pity that the Harlequin Bug, Murgantia histrionica, is widely regarded as an agricultural and garden pest. This member of the stink bug family Pentatomidae is easily one of our most colorful North American insects. I know, I know, tell that to the cabbage farmer.

The fact that I rarely come across this species probably colors my opinion of it toward the rose end of the spectrum. Recently, a contributor to the "Arthropods Colorado" Facebook group page posted images of them in large numbers, so clearly they can be overly abundant at times, in certain places, on certain plants.

The Harlequin Bug is not even native, having moved here from Mexico and Central America (now, now, no illegal immigrant jokes). It was first recorded in the U.S. in Washington County, Texas in 1864, and has since spread northward. Today, it ranges from New England south and west to Colorado, Arizona, and southern California. There have been sporadic records of M. histrionica in northern Illinois, Minnesota, Iowa, and South Dakota.

The adult insect measures 8-11.5 millimeters, and is patterned in black and orange, red, or yellow. Interestingly, I found the specimens in southern California to be almost totally black compared to populations elsewhere, like here in Colorado.

The bright "warning colors," called aposematism in scientific circles, serve notice to potential predators that ingesting the animal wearing that wardrobe could cause sickness or even death.

Like all stink bugs, the Harlequin Bug can secrete aromatic compounds from glands in the thorax when the insect feels threatened. Additionally, Murgantia backs up that warning with toxins that make it very distasteful, especially to birds. Harlequin Bugs feed on a variety of plants, but are partial to those in the mustard family. The bugs take in glucosinolates from those plants as they feed, then use those chemicals for their own defense in a process known as sequestration. Essentially, the bug is unaffected by the plant's chemical defenses, and even hijacks those poisons for its own defense.

Harlequin Bugs do two things very well: eat, and make more Harlequin Bugs. The female bug lays clusters of about a dozen stunning black-and-white banded, barrel-shaped eggs on the host plant. She can lay several clutches in her lifetime, about every three days starting ten days into her adult stage.

Soon, tiny little nymphs emerge from those eggs, disperse, and begin feeding. The nymphs go through five instars (an instar is the interval between molts) before becoming adults. It takes an average of 48 days from egg to adult under laboratory conditions, at an average temperature of 77° F. There may be 3-4 generations of the bug annually, only two in the northern reaches of its range, but up to eight in southernmost latitudes.

Adult females live an average of 41 days, while males endure for around 25. Apparently, the sexes find each other in part from vibrational signals they send through the stems and foliage of the plants they are sitting on.

Murgantia histrionica is not completely invincible. The eggs are attacked by a number to tiny parasitic wasps, namely Ooencyrtus johnsoni, Trissolcus murgantiae, T. basalis, and other Trissolcus species. The Wheel Bug, Arilus cristatus, will prey on the nymphs of the Harlequin Bug, as will the sand wasp Bicyrtes quadrifasciata, the female wasp paralyzing stink bugs as food for her larval offspring in an underground burrow.

Nymphs

Judging by the extraordinary abundance of this species in Colorado this year, I would say the Harlequin Bug prospers in wet years. The preceding years here have been extremely dry, and that may account for their scarcity until now.

Sources: Aliabadi, Alireza, J. Alan A. Renwick, and Douglas W. Whitman. 2002. "Sequestration of Glucosinolates by Harlequin Bug Murgantia histrionica," J. Chem. Ecol. 28(9): 1749-1762.
Canerday, T. Don. 1965. "On the Biology of the Harlequin Bug, Murgantia histrionica (Hemiptera: Pentatomidae)," Ann. Entomol. Soc, Am. 58(6): 931-932.
McPherson, J.E. 1982. The Pentatomoidea (Hemiptera) of Northeastern North America With Emphasis on the Fauna of Illinois. Carbondale: Southern Illinois University Press. 240 pp.
Zahn, Deane K., Robbie D. Girling, J. Steven McElfresh, Ring T. Cardé, and Jocelyn C. Millar. 2008. "Biology and Reproductive Behavior of Murgantia histrionica (Heteroptera: Pentatomidae)," Ann. Entomol. Soc. Am. 101(1): 215-228.

Friday, August 8, 2014

Mini-mantises: Ochthera Shore Flies

Mantids (aka "praying mantises") are widely acclaimed for having the strongest grip among predatory insects, but many other insects have similar modifications to their front legs that afford them a vise-like purchase on struggling prey. Among the more unusual of these are shore flies in the genus Ochthera, found over most of North America.

I was delighted to discover some of these flies recently here in Colorado Springs, where they favor very shallow, trickling streams with algal mats and other debris they can run around on in search of other small insects.

Ochthera are small, only 4-5 millimeters in body length. They are squat and compact, with triangular faces and somewhat protuberant eyes. Their most obvious feature is the pair of front legs, with an enlarged coxa (segment connecting the leg to the thorax), greatly enlarged and muscular femur ("upper arm" if you will), and curved, blade-like tibia ("forearm" comparison to a person). The tarsi ("feet") are of normal appearance. The forelegs are thus raptorial, meaning heavily modified to sieze prey. Spines and tiny teeth on the inside of the femur help anchor the victim between femur and tibia.

The flies easily overpower other small insects such as midges, mosquitoes, and leafhoppers that alight on the shore or the surface of the water. They can also unearth midge larvae from the muck along the shore.

Watch one of these flies and you will see it periodically "stretch," reaching out, flexing, and waving those front legs. This may be a threat display directed at other members of its own species, or a means of recognizing each other and avoiding cannibalism (Simpson, 1975). Females may literally lash out at males attempting to mate with them. Males attempt to mount females from the rear, jumping on top of them and gripping the female's "shoulders" if they are not rebuffed. He sets the mood by rapidly tapping the sides of her abdomen with his hind feet. Actual mating can last at least five minutes, at least in one species (Deonier, 1972).

Mated females lay eggs singly, usually on dead, water-logged, or partly submerged grass stems at the shore or in the shallows. Larvae of Ochthera are aquatic or semi-aquatic, and likewise predatory; they feed mostly on midge and mosquito larvae that they coil around like a snake constricting a rat. They have mouthparts that penetrate the exoskeleton of their prey and feed on soft internal tissues. Larvae progress through three instars (an instar is the interval between molts), before pupating. The pupal stage is also aquatic, equipped with breathing tubes. The larval stages last an average of 7-11 days, the pupal stage about 7-10 days. Egg to adult thus takes about 16-21 days, at least under laboratory rearing conditions.

Look for Ochthera adults from the end of March through the end of October in appropriate habitats. There are thirteen species known for North America, collectively distributed over most of the continent.

Sources: Deonier, D.L. 1972. "Observations on Mating, Oviposition, and Food Habits of Certain Shore Flies (Diptera: Ephydridae)," Ohio J. of Sci. 72(1): 22-29.
Simpson, Karl W. 1975. "Biology and Immature Stages of Three Species of Nearctic Ochthera (Diptera: Ephydridae)," Proc. Entomol. Soc. Wash. 77(1): 129-155. This is an excellent, well-illustrated paper.
Winkler, Isaac. 2011. "Insect of the Week - number 57," Insect Museum, North Carolina State University.

Wednesday, August 6, 2014

The American Pelecinid Wasp

One of the most eye-catching and mysterious wasps in North America has to be the American Pelecinid, Pelecinus polyturator. It is so strange that it is placed in its own family, the Pelecinidae. Furthermore, only the females are commonly seen, leading to speculation that at least temperate climate populations reproduce without males.

I was fortunate enough to encounter live specimens recently, on August 3, at Hudson Gardens in Littleton, Colorado (Arapahoe County). Several had been spotted earlier in the week by nature photographer Alison Kondler, who posted one of her images on the Facebook group page "Arthropods Colorado." The gardens are heavily landscaped, but sit adjacent to the South Platte River. Perhaps the riparian corridor offers the right habitat, or the gardens themselves make for a unique and hospitable ecosystem for this wasp.

There is only the one species known north of Mexico, though there are two others ranging south of the border. Females are hard to miss. They measure 51-62 millimeters in body length, the overwhelming majority of which is the abdomen. Perhaps a better common name for this insect would be "snake-tailed wasp," or "American long-a** wasp." The wasp is wholly glossy black in color. The tibia segment on the hind leg is swollen , giving the wasp the appearance of wearing bell-bottoms.

The single female specimen I observed alighted on a leaf in a shady area and began grooming herself. She would have been the envy of a contortionist, and I wish now I had recorded some video of her gymastics. Insects in general tend to be fastidious groomers, as it is essential to keep their senses sharp, wings aerodynamically sound, and their bodies free of parasites and hitchhikers. Her body plan presents quite the challenge, though, and she had to fold her abdomen in a manner whereby she could rub it with her hind legs.

Before I saw this female, Alison alerted me to a slender black wasp she saw that was out of my view behind another plant. Imagine my shock to find that it was a male pelecinid! Males are exceedingly rare, or at the very least seldom seen. I managed this one shot (below) before he flew off. Male pelecinids measure only 12-25 millimeters, owing to their much shorter abdomen. They are glossy black like females, and also sport the inflated hind tibiae, though that character is not quite as apparent as it is in females. Males historically account for only 4% of collection records for the specis north of Mexico, though there may be a collection bias in that the smaller males are more easily overlooked, or mistaken for ichneumon wasps.

Pelecinus polyturator does not sting. The female uses her long abdomen to penetrate the soil and probe for subterranean scarab beetle grubs. She will lay a single egg on a beetle grub she encounters. Larvae in the genus Phyllophaga ("May Beetles") are the only known hosts. The grubs move vertically in the soil during the year, and are closest to the surface when pelecinids are active, making them perhaps a little easier for the wasps to locate. I can find no information, in a cursory search, as to whether the wasp larva is an internal or external parasite, nor how long the life cycle takes.

Parthenogenesis, the ability to reproduce without fertilization of eggs by male sperm, is not uncommon in some insects; but, thelytoky, the development of a female from an unfertilized egg, is rather rare in Hymenoptera (bees, wasps, ants). Normally, an unfertilized egg yields a male, due to "halplodiploidy," a phenomenon I still cannot wrap my own head around.

You are likely to encounter the American Pelecinid anywhere east of the Rocky Mountains, from southern Canada through the southwest U.S. and all the way to Argentina. In South America, this species has several color and size variations, suggesting more than one species is actually involved.

The adult wasps are most common during the month of August, though they can turn up in July, too. A few persist into September or, rarely, October. Look in the understory of hardwood forests, along woodland edges, and even in city parks.

Sources: Johnson, N.F. and L. Musetti. 1999. "Revision of the proctotrupoid genus Pelecinus (Hymenoptera: Pelecinidae)," J. Nat. Hist. 33: 1513-1543.
Lim, K.P., W.N.Yule, and R.K. Stewart. 1980. "A Note on Pelecinus polyturator (Hymenoptera: Pelecinidae), a Parasite of Phyllophaga anxia (Coleoptera: Scarabaeidae)," Can. Entomol. 112(2): 212-220.
MacRae, Ted C. 2013. "An Elegant Living Fossil," Beetles in the Bush
Mason, W.R.M. 1984. "Structure and Movement of the Abdomen of Female Pelecinus polyturator (Hymenoptera: Pelecinidae)," Can. Entomol. 116(3): 419-426.
Young, Daniel K. 1990. "Distribution of Pelecinus polyturator in Wisconsin (Hymenoptera: Pelecinidae) with Speculations Regarding Geographical Parthenogenesis," Gt. Lakes Entomol. 23(1): 1-4.