Archive for Virginia

A BEVY OF BUCKEYES

Posted in Butterflies, Insects, Virginia with tags , , , , , , on September 15, 2010 by Dr. Art Evans

By Arthur V. Evans

For the past month or so, Virginia has been awash with the Common Buckeye, Junonia coenia. The name Junonia is derived from the diminutive form of the Greek Juno, Zeus’ consort, while the specific epithet, coenia, comes from the Greek kionos meaning common. With six distinct eyespots on their wings, these handsome and energetic insects cannot be confused with any other butterfly species in the Commonwealth.

Their rapid, low, and somewhat erratic flight consists of fluttering strokes occasionally interrupted by meandering glides usually of no more than a foot off the ground. When alarmed, Common Buckeyes are capable of taking to the air in a rapid and sustained flight. They sip nectar from a variety of flowers and frequently rest in open, sunny spots in neighborhoods, parks, wetlands, fields, roadsides, and other open habitats with plenty of low-growing vegetation.

The orange-headed and metallic blue-spined caterpillars are highly variable in color and pattern. They feed on plants in several families and are especially fond of those in the snapdragon (Scrophulariaceae) and acanthus (Acanthaceae) families.

Although they occur throughout the United States, Common Buckeyes only persist in the frost-free southern and eastern halves of the country; individuals observed in the Great Lakes States, New England, and southern Canada are migrants. In eastern United States, these butterflies are in evidence throughout the winter in Florida and the coastal regions of southeastern and Gulf States.

© 2010, A.V. Evans

LUNA MOTHS ARE ON THE WING

Posted in Insects, Moths with tags , , , , , , on April 21, 2010 by Dr. Art Evans

By Arthur V. Evans

The luna moth, Actias luna (Linnaeus). Although the luna moth is native to North America, most of its relatives live in Asia.

Last night, while black lighting for beetles on a cool and still spring night in the Bull Run Mountains in northern Virginia, I was treated to an incredible display of luna moths, Actias luna (Linnaeus). Within an hour of turning on the lights, a baker’s dozen of these marvelously green and ornately tailed creatures had settled on the sheet and nearby tree trunks. Such a sight made me feel quite giddy and brought back a flood of memories of some of my earliest encounters with other spectacular insects as a young naturalist.

The first luna moth that I ever saw in Virginia flew through an unscreened upstairs window. It looked like a soft, green bat as it circled the light at the top of the stairs. It was all that I could do to keep it from being gobbled up by our cats!

They range throughout the hardwood forests of eastern North America. Luna moths were long known to naturalists by the time they were described by Carolus Linnaeus in 1758. The earliest known reference to luna moths in North America was in a note published James Petiver 1700, who had based his comments on a specimen collected in Maryland.

Like other moths and butterflies, the wings of luna moths are covered with scales that make up their colors and patterns.

Luna moths typically emerge from their cocoons in the morning. Powerful fliers, they are often attracted to porch lights and well-lit storefronts. There is only one generation produced in the northern parts of its range and two or three generations are produced in the south. Moths emerging in spring are bright green or blue-green with prominent reddish-purple margins on the outer forewings, while summer broods tend to be more yellow over all with yellowish outer wing margins.

Mating takes place after midnight. Pairs of luna moths sometimes remain coupled until the following evening. Eggs are laid singly or in small batches on upper and lower surfaces of leaves and hatch in about a week. The ravenous and solitary caterpillars feed on the leaves of a wide range of hardwoods, including birch, hickory, walnut, persimmon, and sweetgum. Different populations of luna caterpillars show regional preferences for host plants.

The feathery, or pectinate antennae of the male luna moth are covered with sensory pits that enable to them to detect just a few molecules of the pheromones released by receptive female moths.

Only when they are ready to pupate do the mature caterpillars wander away from the food plant. Cocoons are spun on the ground among the leaf litter at the base of the host tree. Each cocoon consists of a single layer of thin and papery silk that incorporates one or more leaves.

Sightings of the luna moth’s spring brood will still be possible over the next few weeks. Look for them at lights near wooded areas and you just might be treated to a glimpse of one of North America’s most spectacular animal species.

© 2010, A.V. Evans

FALCATE ORANGETIPS

Posted in Butterflies, Environment, Insects, Virginia with tags , , , , , , , on April 5, 2010 by Dr. Art Evans

By Arthur V. Evans

After a few false starts spring has finally arrived here in central Virginia, and not a moment too soon. In hopes of seeing some examples of the early spring insect fauna, I recently set out on a warm, sunny day for the James River Park near the 42nd Street entrance.

The orange and slightly hooked wing-tips were the unmistakable field marks of the male falcate orangetip, Anthocharis midea, the only species of orangetip butterfly found in the eastern United States.

The latest floodwaters from spring rains had only just receded, leaving a thin and dusty film of silt and debris high above the river’s usual channel in the park. Just past the flood residue, small plants had raised their tiny blossoms high to lure the season’s first pollen- and nectar-loving insects.

As I wandered upriver toward the Nickle Bridge, a flash of white with a hint of rich orange crossed my path. It slowly yet deliberately flitted about the freshly emerged sprigs of green that populated the edges of the path before finally settling for just a moment or two on a small flower. The orange and slightly hooked wing-tips were the unmistakable field marks of the male falcate orangetip, Anthocharis midea, the only species of orangetip butterfly found in eastern United States.

The females lack the orange patch, but are otherwise similar in appearance to the males. The wings of both sexes are mostly white; the underside of the hind wing bears a finely marbled yellowish-brown pattern. From tip to tip, their wings span no more than one-and-a-half inches across.

Falcate orangetips are among the first butterflies to emerge from their pupae in spring. Widespread in Virginia, they are found in a variety of habitats, including parks, rocky mountain outcrops, open deciduous and mixed pine-oak woodlands, sandhills, and floodplain forests, especially along stream and river courses.

Females lay their greenish-yellow eggs singly on the flowers of various cresses and other members of the mustard family. The eggs soon turn red and hatch into ravenous larvae that devour mostly seed pods, buds, and flowers, and not leaves. Because of the limited number of reproductive structures on each food plant, larger caterpillars will not hesitate to eat their smaller brethren to reduce competition for meager food resources.

Mature caterpillars are green or blue-green and sprinkled with shiny dark plates bearing short bristles. A yellow stripe runs down the length of the back, while a broad white stripe runs from the head and along each side and meet on its backside. The winter is spent, sometimes two, as a narrow chrysalis that is sharply pointed on both ends.

Don’t hesitate to look for these attractive insects in an open woodland or bottomland forest near you. By early June the falcate orangetips will all be gone, and you will have to wait until the following spring for the next generation to once again make their brief and welcome appearance as heralds of spring.

© 2010, A.V. Evans

TRUE CONFESSIONS

Posted in Centipedes, Environment, Musings with tags , , on April 3, 2010 by Dr. Art Evans

By Arthur V. Evans

Every now and again I am asked what is my least favorite insect or spider. I really don’t have an answer for this question. But I can say, without hesitation, that my least favorite arthropod is the centipede.

Don’t get me wrong. I think that centipedes are fascinating animals, but every time I happen upon one of the larger species in the Order Scolopendromorpha, I can feel the hair on the back of my neck stand up and a cold chill run down my spine.

A centipede has never bitten me, so my discomfiture is not based on personal experience. But I do know what the larger species are capable of in terms of delivering a painful, yet non life-threatening bite with their powerful fanglike front feet, or gnathopods. Combined with their speed and lithe bodies, centipedes just set me on edge.

Scolopendra heros from southeastern Arizona dining on a young mouse. Note the thick, black gnathopod next below the head.

Scolopendra heros, the largest centipede species in the United States, measures in at a whopping 6.5 inches (16.5 cm). They range from central and southern Arizona east to southwestern Missouri, Arkansas, and Louisiana. This species is extremely variable in color. During the summer, adults are active around the clock and are easily seen in the headlights of a moving car as they cross the highway at night with their fore bodies bobbing up and down.

I used to collect these big bruisers to put on display in Insect Zoo at the Natural History Museum of Los Angeles County. While on the road, I checked their containers often to make that the lids were securely fastened. My travelling companions were regularly warned that if a lid accidentally came off and a centipede was on the loose, I would immediately abandon the vehicle.

Yesterday, while collecting beetles in the Zuni Pine Barrens of the Blackwater Ecological Preserve, I committed a potentially serious faux pas in the field by peeling back some loose bark of a dead loblolly pine tree that was leaning directly over my head.

Hemiscolopendra marginata occurs in Missouri, Oklahoma, and Texas east to Virginia and Florida; it is absent in most of the Appalachians.

Out of the corner of my eye, I saw a blue-green centipede, Hemiscolopendra marginata, fall from its once-secure perch, its two-inch long body trunk twisting in the air in an effort regain some sort of foothold. Before I could react, it slid across my forearm to the leaf litter below. Or so I thought.

For several seconds my mind raced. What if it didn’t fall on the ground? What if it or another centipede landed on my shoulder? What should I do? What if it got inside my shirt? My now fevered brain began imagining the centipede sinking it’s gnathopods into the soft and sensitive skin of my neck. Or worse.

I stood perfectly still in the bright spring sun filtering through the tall and slender pines, my body tingling all over in anticipation of anything from a crawling sensation to a stabbing pain. The centipede was nowhere to be felt or found. Still, it took me several more minutes to become convinced that my person was centipede-free and begin to feel a sense of relief.

Recounting this event a full day later still gives me the heebie-jeebies!

© 2010, A.V. Evans

BELLY UP TO THE GRAVEL BAR FOR TOAD BUGS

Posted in Aquatic, Defense, Insects, Predators/parasites/parasitoids, True bugs, Virginia, Virginia State Parks with tags , , , , on March 28, 2010 by Dr. Art Evans

By Arthur V. Evans

One of my favorite haunts for insect photography is a small and unassuming gravel bar located just downstream from the dam that keeps the Swift Creek Lake within its banks in Pocahontas State Park, Virginia.

The toad bug, Gelastocoris oculatus, is widely distributed throughout southern Canada and most of the United States.

Gravel bars are tough places to live. Their surfaces can reach blistering temperatures or be completely inundated by flooding waters. Still, they support insects adapted to live under such harsh conditions that are seldom found anywhere else.

Many larger species spend their days hiding under stones and their nights foraging for food and mates. Some smaller species spend their entire lives comfortably wedged between the narrow, wet spaces between pebbles and coarse grains of sand. And still others are just passing through.

Not long ago, with a rushing stream at my back, I slowly knelt down on thankfully padded knees to recalibrate my focus on this universe wrought small. It took me of bit of time and patience to get my head out of the hustle and bustle of modern-day life, shake off the city with its noise and congestion, and begin to really see and appreciate the tiny inhabitants of this rocky shoal.

Bit by bit I took in my surroundings. Suddenly, a bit of movement drew my eyes toward a small embankment. I kept staring at the spot as I inched toward it, hoping to see whatever it was moving again. But it didn’t. Then it did, and I zeroed in on the spot. Just as the short, warty bug with bulging eyes came into focus, it jumped away. It was a toad bug, Gelastocoris oculatus.

It was as if I had just seen an old friend. I can still remember my very first encounter with this species along the edges of Little Rock Creek that meandered slowly out of the San Gabriel Mountains to the southern fringes of the Mojave Desert in Southern California. This species of toad bug is widely distributed throughout southern Canada and most of the United States.

The rough bodies of toad bugs are usually dull and mottled with brown and black. The base colors range from almost entirely yellowish, reddish-yellow, grayish-black, to nearly black. As a result, toad bugs are masters of the disappearing act.

Their front legs resemble those of a praying mantis, only shorter and chunkier. And like praying mantises, toad bugs are voracious predators and use these legs to capture small insects.

In Virginia, both larvae and adults live gregariously in a variety of habitats along the muddy, sandy, or gravelly margins of ponds, streams, and rivers. Overwintering adults appear in spring to feed and mate.

From May through September each female lays a dozen or so white eggs at a time in the sand, probably 200 or more in their lifetime. The eggs hatch in about two weeks; another two or three months are required before the larvae reach adulthood.

The toad bug eventually abandoned the gravel bar and disappeared into some low herbaceous growth nearby. I turned to find a small coppery ground beetle with bulging eyes, bright green legs, and patches of purple on its back running across the gravel, but this is a story for another time.

© 2010, A.V. Evans

ALTERNATIVE SPRING BREAK AT THE VCU RICE CENTER

Posted in Education, Environment, Insects, VCU Rice Center, Virginia with tags , , on March 26, 2010 by Dr. Art Evans

By Arthur V. Evans

© 2010, J. Barton

Last week, I met a group of very dedicated and enthusiastic students from the Virginia Commonwealth University and Virginia Wesleyan College at the VCU Rice Center in Charles City County. They had spent the last several days participating in various activities as part of this year’s Alternative Spring Break. Sponsored by the Chesapeake Bay Foundation, Alternative Spring Break provides students with an opportunity to explore and give to their community by providing a week’s worth of environmental and conservation projects, such as planting trees, tending gardens, tidying  up parks and wildlife refuges, and stream cleanups. At the Rice Center, some of the students would have the opportunity to help me with my insect survey.

© 2010, J. Barton

After an impromptu presentation about my survey and some of the methods used to trap insects, my team of volunteers was ready to get started. They grabbed tools and traps and set out for the first trap site. Working like a well-oiled machine and with minimal direction, they quickly established two sets of Malaise, Lindgren, and pit fall traps in less than two hours.

Malaise trap. © 2010, A.V. Evans

What is a Malaise trap you ask? It’s like a tent with its walls on the inside and is specifically designed to capture flying insects, day or night. Upon hitting the internal nylon panels, most insects will eventually work their way up into a collecting container partly filled with alcohol. Malaise traps are usually used to catch flies, bees, and wasps, but other kinds of insects are captured, too. They are typically placed along roads, trails, streams, or forest edges. Up to 1,000 insects a day may be captured in a good site.

Lindgren funnel trap. © 2010, A.V. Evans

Lindgren funnel traps are designed to attract and capture wood-boring beetles and other insects that alight on tree trunks. They consist of a rain and debris guard with a dozen black plastic funnels suspended directly underneath. Attached to the bottom funnel is a specimen receptacle. Each trap is fitted with chemical lures that simulate the odors given off by dead and dying trees. Insects attempting to land on the trap fall down the funnels and into the receptacle at the bottom. Foresters use Lindgren funnel traps to monitor pest insects in stands of managed timber, especially bark beetles.

Pit fall traps connected by drift fences of metal flashing capture small crawling animals,

Pit fall traps. © 2010, A.V. Evans

especially insects and other arthropods. At the end of each drift fence is a single pit fall trap consisting of two 16-ounce plastic drink cups nested in one another and sunk so that the tops are flush with the soil surface. The inner cup is partly filled with environmentally “friendly” antifreeze (propylene glycol). Each cup is covered with 1/2” mesh and flashing to keep out both vertebrates and rain.

© 2010, A.V. Evans

Thank you so very much to all the students who joined me on that wonderful day. Not only did you help get the job done, you also inspired me with your camaraderie, energy, and sense of purpose.

© 2010, A.V. Evans

MANTIDFLIES GET A LEG UP ON SPIDERS

Posted in Insects, Predators/parasites/parasitoids, Virginia with tags , , , , , on March 17, 2010 by Dr. Art Evans

By Arthur V. Evans

A few years back, on a warm muggy evening in September at the Savage Neck Natural Area Preserve on the Eastern Shore of Virginia, I was checking a light trap designed specifically to lure night-flying insects. As the beam of my headlamp swept over nearby shrubbery, my eye caught a pale green insect just over half an inch long perched on a leaf.

The green mantidfly, Zeugomantispa minuta, looks like a cross between a green lacewing and a praying mantid. They live throughout much of eastern United States and are found in a variety of habitats from late June through early October.

With four clear wings folded rooflike over its body and a pair of grabbing forelegs held tightly against its long, slender thorax, this animal looked like a cross between a green lacewing and a praying mantid. In fact, it was the green mantidfly, Zeugomantispa minuta.

Mantidflies belong to the order Neuroptera and are only distantly related to mantids. Instead, they are related to antlions (whose larvae are known as doodlebugs), lacewings, and owlflies. Praying mantids are in the order Mantodea and are actually cousins of cockroaches.

Adult mantidflies capture and eat all kinds of small insects in captivity, but little is known of their food preferences in the wild. The larvae are also predators. Some are known to attack the pupae of moths, or the larvae of beetles, flies, bees, and wasps, while others prey on the eggs of spiders.

There are two basic strategies for mantidfly larvae to successfully dine on spider eggs; they are either egg sac penetrators or spider-boarders. Egg sac penetrators, such as those of green mantidflies, seek out their food directly.

When they find an egg sac they chew their way through the silk casing with highly modified jaws. The grooved mandibles and maxillae fit snugly together to form a pair of piercing/sucking tubes through which they draw out the embryonic fluids of the eggs.

Spider boarders are unable to chew their way inside spider egg sacs. Instead, they seek out a female spider, climb onto her body, and wait. What are they waiting for? Egg-laying day. The larvae disembark just in time to be wrapped up with the eggs in the egg sac.

Those mantidlfy larvae that initially hitched their fortunes to a male must eventually switch to the egg-producing sex. They switch hosts either while the male is mating or being cannibalized by a female.

The life cycle of mantidflies is a type of complete metamorphosis known as hypermetamorphosis. The first larval stage is quite active and resembles a slender, leggy silverfish, a body type that serves them well as they seek out egg sacs or spiders. Once inside the egg sac, the larva switch into feeding mode and go through two  grublike stages before completing their development into adulthood. These fat, short-legged larvae are decidedly more sedentary. Afterall, they are thorax deep in food and have no need to go anywhere.

One of the most amazing things to me about mantidfly natural history is that scientists figured it out at all. The seemingly unlikely relationship between mantidflies and spiders was first described in 1869 and, with careful and patient study, continues to unfold today. It is this unrelenting promise of discovery that keeps me and my colleagues forever enamored with the world of insects and spiders and dreaming of an endless summer.

© 2010, A.V. Evans

WINTER DARK FIREFLIES

Posted in Beetles, Defense, Insects, Virginia, Winter with tags , , , , , , , on March 15, 2010 by Dr. Art Evans

By Arthur V. Evans

Today was cool, gray, and blustery–not exactly what I would call ideal conditions for finding insects. Nevertheless, I set out for the woods along Jordans Branch in Bryan Park here in Richmond, Virginia in hopes of finding early spring species to photograph. I ambled down a trail through a stand of holly toward a mixed woodland of loblolly pine and various hardwoods. As I knelt down to inspect the trunk of a pine snag, a faintly beetlish outline partially hidden in a crack in the bark caught my eye.

The winter dark firefly, Ellychnia corrusca, is mostly dull black with yellow, orange, or reddish arched bands along the sides of their midesection.

It was a winter dark firefly, Ellychnia corrusca. Flat and soft-bodied, the beetle measured slightly more than one half inch in length. It remained motionless until I gently coaxed it out of its hiding spot with a pine needle for a better look.

Winter dark fireflies are mostly dull black, but the sides of their flattened, shield-like midsections are marked with yellow, orange, or reddish arched bands. Their soft, pliable wing covers are clothed in short, fine, golden hairs.

Mature larvae pupate in dead logs, especially pines. Adults emerge in late summer and fall and are sometimes encountered on trees or on the flowers of goldenrod and other asters. As temperatures begin to drop, they seek protected places under bark for the winter. The beetles reappear on late winter and early spring days, either resting on bark or circled around sap flows on maples like cattle around a trough.

Like their more familiar cousins of summer, winter black fireflies are bioluminescent, at least for a while. Both the larval and pupal stages produce their own light. Even freshly emerge adults maintain this youthful glow, but as the beetles grow older they lose their light-producing organs.

Mating winter dark fireflies are not an uncommon sight. Their courtship involves two stages. First, the male climbs on the back of the female while constantly touching her with his antennae and mouthparts. This activity alone may last for up to half an hour. Afterward, the couple consummates their relationship by joining their bodies as they face away from one other. Sometime during the next hour or so, the male transfers a protein-packed packet, or spermatophore, to the female. Pairs of beetles sometimes remain joined together this way for up to an entire day. Over the next several days the female will slowly digest the spermatophore inside her body and store it as a source of energy in her body. Both males and females will mate several times before dying in late spring or early summer.

When attacked, these beetles exude a bitter fluid from their leg joints. This defensive strategy, known as reflex bleeding, is also practiced by other species of lightningbugs.In spite of their chemical defenses, phorid flies attack winter dark fireflies and their kin. Just how the flies locate their hosts is unknown, but their maggots develop inside the beetle, killing their beetle host as they emerge to pupate.

Recent studies suggest that winter dark fireflies are not a single species, but represent a complex of closely related, yet undescribed species that inhabit most of eastern North America. The taxonomy and natural history of these handsome, delicate, harbingers of spring would make an excellent study for a student looking to make a significant scientific contribution to the study of North American beetles.

© 2010, A.V. Evans

HUBBARD’S ANGEL INSECT

Posted in Insects, VCU Rice Center with tags , , , on March 8, 2010 by Dr. Art Evans

By Arthur V. Evans

My step-son Graham Wilson and I drove out to the VCU Rice Center in Charles City County, Virginia this morning in search of insects to photograph. By late morning, the temperature was in the high 50’s and the only insect seen on the wing was a single mourning cloak. Undaunted, I began searching for snags and logs with loose bark.

With Graham looking on, I slowly peeled back a slab of bark from a large fallen oak. I soon caught a glimpse of several tiny, pale insects less than 1/8 inch (2.0-3.0 mm) long as they scurried about the smooth, moist patch of exposed wood. I immediately recognized the wingless, termite-like animals as angel insects, or zorapterans. They quickly scrambled to find a dark nook or cranny to escape the sudden invasion of light.

Hubbard's angel insect, Zorotypus hubbardi, is one of two species of zorapterans found in the United States.

Angel insects are not rare and are sometimes quite abundant locally. They simply escape attention because they are small, secretive, and easily overlooked. Adults are most active in spring and summer and are typically found in deciduous woodlands. Here in Virginia, I usually find them under the bark of rotten logs, often in association with moist accumulations of termite frass.

The order Zoraptera was proposed in 1913 by the Italian entomologist Filippo Silvestri. The name of the order is derived from the Greek words zoros (sheer or pure), a, without, and pteros (wing); winged zorapterans were discovered after the name of the order was proposed. Of the 32 species of angel insects known worldwide, most are tropical. Only two are found in the United States: Hubbard’s angel insect, Zorotypus hubbardi Caudell (eastern United States) and Snyder’s angel insect, Z. snyderi Caudell (southern Florida).

Hubbard’s angel insects are gregarious and live in small groups; isolated individuals are incapable of surviving for very long on their own. They are usually found under the bark of rotting logs, where they eat fungus, especially spores and the branching, threadlike fungal structures known as hyphae. Dead nematodes, mites, small insects and other minute arthropods are also scavenged when there is an opportunity. In the laboratory, angel insects thrive on a diet of yeast and crushed rat chow, as well as their own remains.

Angel insects spend much of their time grooming themselves or each other. They reproduce sexually or by parthenogenesis. Before mating, males court females by offering them droplets of fluid secreted by a special gland on their head. Receptive females mate for several days with the same or different partners. Soon they will lay batches of eggs, cover them with chewed bits of food, and watch over them for several weeks until they hatch. The larvae resemble small versions of the adults and molt four or five times before reaching maturity. The larvae are distinguished from the adults by their smaller size and eight-segmented antennae.

Most angel insects are pale, wingless, and blind. Their eyeless, triangular heads are equipped with chewing mouthparts. Adults have pair of antennae with nine bead-like segments. Their hind legs are equipped with bulging thighs armed with a row of small, sharp spines underneath. All six zorapteran feet are two-segmented, the first of which is very short.

Tough times as a result of overcrowding or dwindling food supplies trigger the production of eyed and winged males and females that soon take to the air in search of better living conditions. Their four transparent wings resemble narrow paddles and have few supporting veins. Although similar in shape, the forewings are distinctly longer than the hindwings. Zorapterans are often attracted to lights on warm nights. Like termites, they shed their wings easily upon entering a new log, leaving only four small stubs behind.

Zorapterans have stumped systematic entomologists for years in terms of trying to sort out their relationships with other insects. Unfortunately, their currently sparse fossil record has yet to shed any light on the subject. Originally considered the nearest relative of termites, zorapterans have since been allied with termites + cockroaches, earwigs, earwigs + cockroaches + mantids, thrips, or barklice.  Currently, they are considered as closely allied with another curious group of insects, the webspinners (Embioptera).

© 2010, A.V. Evans

THE FOREST CATERPILLAR HUNTER, Calosoma sycophanta, IN VIRGINIA

Posted in Beetles, Environment, Insects with tags , , , , , , , on February 24, 2010 by Dr. Art Evans

By Arthur V. Evans

In July of 2008, while conducting a beetle survey of the Bull Run Mountains Natural Area Preserve in Fauquier and Prince William counties in Virginia, I found numerous metallic green elytra scattered along a foot trail winding through an oak woodland on a west-facing slope. The area had been heavily infested with larvae of the gypsy moth, Lymantria dispar, as evidenced by thousands of larval exuviae and pupal cases that festooned the trunks of oaks and other hardwood trees.

At first glance, I thought the beetle remains were those of the indigenous caterpillar hunter or fiery searcher, Calosoma scrutator, a common, brightly colored, and widespread carabid beetle found in the mountains and lowlands of Virginia. Closer inspection revealed that the elytra were much brighter and more yellow than those of C. scrutator and lacked the characteristic coppery red margins.

Further searching in the area produced a very fragile, yet nearly intact specimen ensnared in an abandoned spider web. The pronotum of this specimen was mostly black with metallic blue along the margins, rather than bluish with violet or coppery yellow green borders typical of C. scrutator. Of the five other species of Calosoma known in Virginia, only C. wilcoxi has entirely metallic green elytra, but it is smaller and much duller than either C. scrutator or the silk-wrapped remains in question. (Figure 1).

Figure 1. The Virginia species of Calosoma (from top to bottom, left to right): C. calidum (F.), C. externum (Say), C. frigidum Kirby, C. sayi Dejean, C. scrutator F., C. sycophanta (L.), and C. wilcoxi LeConte. The scale bar equals 5.0 mm. © 2009, Chris Wirth.

I soon realized that what I had in my possession were the remains of a European species, the forest caterpillar hunter, C. sycophanta. Long known as an important predator of gypsy moth larvae in France, 4,046 of these beetles were imported into the United States between 1905 and 1910, most of which were released in New England to combat outbreaks of two European species of lymantriids: the gypsy moth and the browntail moth, Euproctis chrysorroea.

In the United States, the forest caterpillar hunter is established in Connecticut, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Rhode Island, Vermont, and Washington. They have been released in Delaware, Michigan, Washington, and West Virginia, but they have yet to become established in these states. In spite of releases on Vancouver Island, British Columbia, Quebec, New Brunswick, and Nova Scotia, the forest caterpillar hunter does not appear to be a permanent resident in Canada either.

Both the adults and larvae climb trees to attack and eat caterpillars and pupae of gypsy moths and other species. Adult males are more likely to be found on tree trunks, while females tend to remain on the ground. Based on observations in the laboratory and in the field, both sexes are active day and night. Males tend to be more conspicuous as they spend most of their time actively searching for mates. The more secretive females spend much of their time buried in the soil and hidden among leaf litter to feed and lay eggs.

Adult activity coincides with the larval activity of the gypsy moth. Beetles emerge from their overwintering sites in June to search for prey and mates, although some beetles may remain dormant for up to two years. Although adults are strong and agile fliers capable of leaving their overwintering sites behind to search for high populations of caterpillars, their appearance at new outbreaks of gypsy moths is by no means certain. In fact, beetles released as part of biological control programs often remain near their release site.

Forest caterpillar hunters will attack a variety of other caterpillar species, but are most abundant where populations of gypsy moth caterpillars are high. They remain active for about a month, re-enter the soil, and remain there until the following spring.

Adult predation is not this species’ primary impact on gypsy moth populations. It’s greatest impact is through larval production and the voracious appetites of the beetle’s larvae for mature caterpillars and pupae. The ability of adult beetles to reproduce is directly dependent upon the availability of high densities of gypsy moth caterpillars, especially since females require sufficient protein to ensure successful development of their eggs.

Eggs are laid in the soil beginning in early July and hatch in 4-7 days. The larvae climb trees in search of caterpillars and pupae. The remains of pupae attacked by beetle larvae have characteristically large and jagged holes. Mature beetle larvae seek pupation sites in the soil. The entire life cycle, from egg to adult, takes about seven weeks. In Connecticut, adults are known to live three to four years.

Anecdotal evidence suggests that forest caterpillar hunters are potentially important predators of gypsy moth larvae and pupae, but there is still much to learn. Nearly all of the information on the ecology and behavior of C. sycophanta was gathered during the brief period of adult activity that coincides with gypsy moth outbreaks, but little is known about the ecology of this species between outbreaks.

Many thanks to Chris Wirth for the wonderful color plate. This essay is excerpted from Evans, A.V. 2010. The forest caterpillar hunter, Calosoma sycophanta, an Old World species confirmed as part of the Virginia beetle fauna (Coleoptera: Carabidae). Banisteria [2009] 34: 33-37. The full article is available at http://fwie.fw.vt.edu/VNHS/banisteria/banisteria.asp.

©2010, A.V. EVANS

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