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.

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.

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.

This specimen is from Baker Wetlands near Lawrence, Kansas

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.

Ant-hunting spider, Euryopis

To look at a specimen of the genus Euryopis, you would hardly imagine that it is a member of the cobweb weaver family Theridiidae. Apparently it has physical characters that place it there, but when it comes to behavior, this spider departs radically from its tangled-web weaving cousins

I was invited to participate in an informal "bioblitz" back on June 22, 2014, in the upper reaches of the Monument Creek watershed here in El Paso County, Colorado, an elevation of 8,500-9,000 feet. Among our small party were several botanists, one of whom brought me a couple of spiders she found while looking at plants. One of those spiders was a gravid (egg-laden) female Euryopis that I brought home to take better images.

Euryopis is placed in the subfamily Hadrotarsinae of the Theridiidae family based on shared characters like a high carapace (top of cephalothorax) that is nearly as wide as it is long; exceptionally long, flat fangs; certain anatomy of the female genitalia; and the fact that these spiders do not spin prey-catching webs.

There are about twenty species of Euryopis recorded for North America north of Mexico, and all of them are very small. Both genders range from only 1.3-4.7 millimeters in body length, males slightly smaller than females. Most species share the unique sub-triangular shape and bold color pattern on the abdomen as demonstrated by the Colorado specimen shown here.

Typical ambush pose

What is truly amazing about these spiders is their hunting technique. They simply sit with legs outstretched, either on the ground, foliage, or tree trunk, and wait for an ant to brush against them. This triggers a response on the part of the spider, whereby the arachnid runs around the ant, all the while flinging silk from its spinnerets and bonding the ant to the surface of the substrate before the insect knows what happened.

Once the prey is immobilized, the spider bites it, usually on a leg joint, and waits while the venom takes effect. The spider then fashions a silk "sling" that it uses to haul the victim to a place where the spider can feed without disturbance from other ants.

Ants are aggressive and pretty vicious, so few predators bother them. It is a testament to the toughness of Euryopis to mess with them. At least one species feeds almost exclusively on harvester ants, which are among the most pugnacious of all North American ants, equipped with stingers that they deploy without hesitation (Porter and Eastmond, 1981)

My little female spider soon spun an egg sac in captivity. The size of the bundle was surprising considering how small the spider was. It was white, hemispherical in shape, and covered in little tufts of silk as shown in the image above

Euryopis are probably not uncommon spiders, but easily overlooked due to their diminutive size and rather cryptic appearance when presented on the ground or other natural surface. Try seeking them out around ant mounds and places where ant traffic is high.

Sources: Adams, R.J. 2014. Field Guide to the Spiders of California and the Pacific Coast States. Berkeley: University of California Press. 303 pp.
Agnarsson, Ingi. 2004. "Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)," Zool. J. Linn. Soc. 141: 447-626
Bradley, Richard A. 2013. Common Spiders of North America. Berkeley: University of California Press. 271 pp.
Porter, Sanford D. and David A. Eastmond. 1981. "Euryopis coki (Theridiidae), a spider that preys on Pogonomyrmex ants," Research Notes in J. Arach. 10: 275
Ubick, D., P. Paquin, P.E. Cushing, and V. Roth (eds.). 2005. Spiders of North America: an identification manual. American Arachnological Society. 377 pp.