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Leaves and buds of Brazilian fire tree are transported from the treetop to the colony by major workers.

Last week we traveled to Costa Rica and met a captivating caterpillar in the tropical rainforest. Over the next several weeks, we will visit several species of ants, so called superorganisms of the tropical rainforest, creatures with social structure and specialized roles that, as individuals, cooperate and contribute to the success and survival of their colony. It has been said that on planet earth only two creatures cultivate crops: humans and ants. So, let’s return to the tropical forests of Costa Rica to visit these farmers who are the most important group of herbivores found in tropical forests in the New World, leafcutter ants.

Leaves of a small shrub are disassembled by powerful jaws of major workers. Figuring out just the right way to carry the leaf is tricky business, but once lifted overhead, it’s off to the races and back to the colony.

Night and day members of the worker caste search for nutritious leaves on trees, vines, and shrubs. When scouts find a suitable food source, they direct other workers to the bounty by releasing trail-marking chemicals called pheromones. The amazing jaws of major workers clip small sections of leaves and flowers and carry them to the ground, where they join a rambunctious procession of nest mates. In this parade, intermediate sized workers busily transport leaf sections while smaller workers sometimes hitchhike on leaves and help defend their sisters from marauding predators and parasitic flies. Nearby, large imposing soldiers also defend their sisters and the colony with powerful jaws. As leafcutters remove foliage from a tree, a parade of ants may extend for distances of more than 200 yards as workers carry leafy cargo back to a subterranean nest.

On a nearby tree, flowers and flower buds travel to the ground. Transporting flowers seems relatively easy, but carrying a bud seems to be a challenge. Watch a worker as she finally figures out how to haul a flower bud. Amidst the hustle and bustle of the ant trail, blossoms disappear underground to fuel the nutritious fungus garden.

Ventilation shafts cool the underground ant colony and provide for the exchange of gasses.

A leafcutter nest is a marvelous structure that may contain several million ants and occupy 600 square meters of forest floor. Sophisticated ventilation systems cool the bustling nest and allow carbon dioxide to escape while drawing in oxygen. Once inside the nest, leaves are delivered to other workers that take the leaf sections and clip them into ever smaller fragments. These fragments are carefully inserted into a garden of living fungus maintained by the ants. Leaves serve as a substrate for fungi, which is harvested as the source of food for the entire ant colony. The fungus garden is meticulously tended by workers. Destructive alien fungi are detected and removed. Secretions produced by the queen and workers facilitate the growth of the cultivated fungus. Fungal strands produce specialized structures called gongylidia. Gongylidia are fed to the developing larvae and distributed throughout the colony to feed workers and the queen. Due to their agrarian life style, leafcutter ants are also commonly called fungus growing ants.

Sharp jaws of the major worker are used not only for cutting leaves but also for defending the colony from vertebrate predators and foolish bug geeks.

Leafcutters don’t leave much behind when defoliating favored plants.

To support their enormous colonies, leafcutters remove vast amounts of vegetation each day. It is estimated that large colonies may remove more than 500 dry weight pounds of vegetation annually. When nests are established near orchards or crops, leafcutters can strip trees and vegetables overnight, causing significant crop loss. Often, irate farmers destroy leafcutter colonies. One humorous account related by Hölldobler and Wilson of a westerner’s attempt to grow a European style vegetable garden in Belize reported that the gardener “… arose one morning and found our garden defoliated: every cabbage leaf was stripped…of the carrots nothing was seen…into a hole in the mound, ants, moving in quickened step, were carrying bits of our cabbage, tops of carrots, the beans – in fact our entire garden was going down that hole.” However, leafcutter ants play a vital role in recycling plant material and enriching and cultivating tropical soils. For millennia in tropical jungles throughout the New World, legions of leafcutters have been the consummate farmers in the rainforest.

Acknowledgements

Bug of the Week thanks Costa Rica Vacations and the intrepid guides Mono and Kenneth at Rafiki Lodge and Ale at Playa Cativo Lodge for providing the inspiration for this episode. The wonderful book “The Ants” by Bert Hölldobler and Edward O. Wilson was used as a reference.

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Silk moth caterpillars like this Automeris species are spectacular denizens of the rainforest.

With the return of warm weather, leaves, and insects still weeks away here in the DMV, it’s time to travel to tropical rainforests in Costa Rica to see what’s up with some of our southern neighbors. First stop is the rainforest near the village of Santo Domingo bordering the Savegre River in Costa Rica. Scrambling across the ground near the base of a tree was a magnificent caterpillar. At first glance the identity of this beauty had me stumped, but after picking it up fiery stings to my finger and palm refreshed my memory of its true identity. This caterpillar is a member of the silk moth clan in the genus Automeris. The remarkable color pattern of this extraordinary larva leads me to believe its identity is Automeris metzli, a creature found from Mexico to Ecuador and also on the island of Trinidad, where it munches leaves of oak and less commonly Erythrinaand coconut.

Don’t let these amazing spines and beautiful colors fool you. Handling this lovely caterpillar could result in a spicy and memorable surprise.

False eyespots on the hind wing may help beautiful male (top) and female (bottom) Automeris moths gain protection from hungry predators. These two are Io moths, Automeris io.

You might think that a very large (this one was several inches long) tasty caterpillar would attract the attention of hungry predators. But Automeris caterpillars have a clever defense. Lining their sides and backs are spines loaded with venom. These spikey armaments are called urticating spines. Upon contact by a predator or overcurious human these spines release venom, causing a painful and relatively long lasting sting. For most people this sting resolves without complication but for some it may cause a serious allergic reaction. For me, well, getting up close and personal with this creature was worth some minor discomfort. Urticating spines are employed for defense by several families of moths, including flannel moths and saddleback caterpillars we met in previous episodes. While stinging shock and awe are the defensive syndrome employed by these caterpillars, adult moths use a different strategy. When resting on vegetation or on the ground, the brownish dappled forewings of the moth help it blend with background vegetation, effectively camouflaging the moth. If a predator draws too near, the moth spreads its forewings revealing large vertebrate eyespots on the hindwings. This ruse is thought to startle and frighten would-be predators, allowing the moth to escape or break-off the attack. False eyespots have evolved many times in the insect world and are found on caterpillars including swallowtail caterpillars, Promethea moths, and owl butterflies we met in previous episodes.

A cousin of Automeris metzli called the Io moth is relatively common in much of North America. including the DMV. This beautiful species of moth was once very abundant from New England to the Gulf States and west to the Great Plains. However, in New England and throughout much of its range, Io moths have declined. In addition to loss of natural habitat, the introduction of the parasitic fly Compsilura concinnata to control gypsy moth caterpillars has been implicated in local and regional declines in populations of Io moths and several other moth species attacked and killed by the fly. Habitat destruction and invasive species are but two threats to these charismatic and beautiful creatures throughout their ranges.

Acknowledgements

Bug of the Week thanks Hugh and Bridgette for discovering the gorgeous caterpillar, Costa Rica Vacations, and the intrepid guides Mono and Kenneth at Rafiki Lodge, for providing the inspiration for this episode.  “Automeris metzli Sallé (Lepidoptera: Saturniidae) in Trinidad, West Indies” by Matthew J.W. Cock, “Moth decline in the Northeastern United States” by David Wagner, and “Insect Defenses” by T. Eisner, M. Eisner, and M. Siegler, were used as references for this episode.

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On hot days with brilliant sunshine a dragonfly may point its abdomen upward to reduce the surface area exposed to the sun.

This week we continue our adventures in the aquatic realm where we recently visited whirligig beetles and water striders. Now let’s meet some tiny dragons. Dragons are mythological beings common to many cultures. These fanciful and fearsome predators are often chimeras of several creatures with wings of a bat, head of a reptile, scales of a fish, feet of an eagle, or tail of a serpent. With enormous compound eyes, reticulate wings, long legs, and a snaky tail, dragon seems a fitting name for the insects we call dragonflies.

Dragonflies belong to a group of flying insects called the Anisoptera. The name Anisoptera comes from the Latin roots aniso- (meaning unequal) and –ptera (referring to wing). Anisoptera is a reference to the fact that the forewings of dragonflies are not nearly as wide as the hindwings. Dragonflies are an ancient clan. Those patrolling the skies 250 million years ago had wingspans of two and a half feet. Modern dragonflies are smaller but no less magnificent. They are active predators hunting and capturing prey while on the wing. Spiny legs held beneath the body in a basket-like arrangement trap victims. Small insects such as mosquitoes or crane flies are common snacks, but larger insects including bees, butterflies, and other dragonflies or damselflies may be captured. There are reports of large dragonflies catching hummingbirds.

On a chilly day in February it’s nice to think about a warm summer day when a dragonfly might choose a dragonfly ornament to perch upon amongst zinnias in my flowerbed. But dragonflies are fierce predators. Watch as a dragonfly devours a damsel in extreme distress – damselfly that is.

An empty shed skin attached to a stem is all that remains of a dragonfly’s life underwater.

Male dragonflies often patrol specific territories along ponds or streams on the lookout for food, potential mates, or other males. Other males entering a territory are pursued and driven away. Females are wooed and mating pairs of dragonflies are often seen flying in tandem. The male sometimes guards his mate while she deposits eggs in the water or on aquatic vegetation. Eggs hatch into fascinating submariners called nymphs. These beautiful swimmers live in ponds or streams obtaining oxygen from the water through gills found inside their anus. Muscular contractions allow the nymph to pump water in and out of its rear-end to breath. How curious!

Dragonfly nymphs capture many kinds of insects such as the larvae of aquatic beetles, midges, and mosquitoes. Yes, dragonfly nymphs are important predators that help hold mosquitoes at bay. Crustaceans, worms, tadpoles, and even small fish are fair game for these stealthy hunters. Dragonfly nymphs sit and wait for a potential meal to come near. When in range, a remarkable, hinged mouthpart snaps forward like a bullfrog’s tongue to ensnare the victim. Nymphs usually move about by crawling slowly. However, when startled or under attack, they expel a blast of water from their rear ends and are propelled forward like a jet. After molting several times and completing development, a nymph will climb out of the water and attach itself to a plant or stone. The nymphal skin splits and the adult dragonfly emerges. Once the exoskeleton has hardened, the daring aerialist will take wing to hunt, mate, and entertain lucky humans on a warm summer day.

The insect on the left with gills on its tail is a damselfly nymph. The insect more centered is a dragonfly nymph. Watch mosquito larvae disappear into the maw of the dragonfly nymph, captured by the lightning strike of the nymph’s hook-bearing mouth-parts. Clips at normal speed have been slowed by 85% to observe prey captures.

Acknowledgements  

We thank Bill Lamp for providing the gorgeous dragonfly nymphs featured in this bug of the Week. Information was gleaned from “An Introduction to the Study of Insects” by D.J. Borer, D.M. De Long, and C.A. Triplehorn, “Beginner’s Guide to Dragonflies” by B. Nikula, J. Sones, D. Stokes and L. Stokes, and “Eco-Friendly Control of Mosquito Larvae by Brachytron pratense Nymph” by S.N. Chatterjee, A. Ghosh, and G. Chandra. 

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What forces and clever adaptations enable water striders to literally walk on water?

Last week we visited whirligig beetles and learned their secrets of living at the intersection of water and air. This week we return to the water to visit another member of the neuston, the interesting community of organisms that spend their lives on or near the surface of water. Gerrids go by a number of colorful common names including water striders, pond skaters, and Jesus bugs owing to their remarkable ability to walk just a few millimeters above the water’s surface. One fine autumn afternoon along a gentle stream in the Blue Ridge Mountains I happened upon a nice collection of water striders scooting across the surface of a small pool. Water striders are predatory members of the true bug clan that includes terrestrial predators such as wheel bugs and spined soldier bugs we met in previous episodes. These aquatic predators dine on small insects and other arthropods, either living or dead, whose fortunes deposit them on the water’s surface. Powerful jaws are used to penetrate the exoskeleton of a victim while needle-like stylets inject proteolytic enzymes to
liquefy internal structures of the prey. A pump in the head of the water strider sucks the nutrient-rich liquid into the predator’s digestive tract. Yum.

The majority of water striders are denizens of fresh water but a few live in brackish waters or truly saline waters of the ocean. As a group, they have evolved remarkably clever strategies for dealing with the uncertainties of aquatic life. Those utilizing large permanent water sources like lakes may lack wings entirely and forgo the ability to fly, putting their bodily resources into reproduction rather than mobility. Others found in temporary water sources often have winged individuals capable of escaping vanishing pools and colonizing new water-filled ones.

Small dimples in the water caused by cohesion of water molecules beneath each of six widely spread
legs distribute the strider’s weight, enabling it to stand and zoom across the surface without sinking.

Perhaps the most interesting aspect of water strider life is the unique ability to walk on the water’s surface. Here’s how they do it. The body of the water strider is covered with thousands upon thousands of fine hairs. The larger of these dense hairs covering the body repel water, keeping the strider from becoming water-logged and sinking when splashed or submerged by a tiny wave or pelted by raindrops in a downpour. The real magic comes by way of tiny microhairs found at the tips of the water striders legs. These can number more than a thousand hairs per square millimeter. By distributing its weight across six legs, each with water repellent hairs, the water strider takes advantage of the cohesive force of water molecules. Water molecules
simply stick together due to the attraction of one charged molecule to another. This cohesion causes the water to form small depressions beneath each leg as it bears the weight of the insect. To move forward, the water strider shifts minute amounts of weight to one of the middle legs and then pushes against the back wall of the depression thereby propelling itself forward. By alternating movements of the middle legs, steering with the hind legs, and carefully distributing its weight among all legs, the strider walks on water. One can only imagine what fun could be had if we had skates or shoes to exploit the cohesive force of water molecules.   

Acknowledgements

Two wonderful references “Aquatic InsectEcology” by J.V. Ward and “Insect Ecology” by P.W. Price, R.F. Denno, M.D.Eubanks, D.L. Finke, and I. Kaplan were used to prepare this episode.  

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Viewed from the side you can see compound eyes of the whirligig beetle, one looking up, another looking down. Two on the right and two on the left make four. But the question is why?

Having crossed the optical threshold of unaided vision many years ago, I find having four eyes – that is, wearing glasses – to be incredibly useful, especially when trying to observe the antics of very small creatures like insects. In this week’s episode we meet a fascinating beetle with four eyes. No, it doesn’t wear glasses, although that would be pretty funny, but it really does have four eyes. Beetles in the family Gyrinidae, commonly known as whirligig beetles, live the life aquatic at the interface between the world of air and sunlight and the world of swirling water. The name whirligig stems from their habit of swimming rapidly and changing direction frequently, often in circular patterns.  Some observers comment that these beetles seem to gyrate on the water’s surface.

Life at the interface of two worlds, one of air and the other of water, presents interesting challenges. One challenge of course is the very different way light passes through water compared to its passage through air, and how this difference affects vision. Many of us have had the interesting experience of observing aquatic creatures underwater at an aquarium or through the lens of a dive mask. You’ve seen that objects appear significantly larger underwater than when viewed in air. This phenomenon results from water refracting or bending light as it moves through water, making objects appear about one third larger than they actually are. Imagine the dilemma of a surface dwelling insect faced with the prospects of attempting to keep an eye open for predatory fish lurking below while simultaneously monitoring for hungry birds ready to pounce from above. Whirligig beetle have a unique solution to this visual dilemma. They have evolved two unique sets of eyes, one pair gazing upward above the water’s surface, one downward-looking pair immersed in the water below.  

Sneaking up on a raft of whirligigs plying the gentle currents of the Gunpowder River, the beetles appear orderly and intent on holding their place in the current. But with a quick wave of my hand, whirligigs quickly shift into the swirling, dizzying, pandemonium from which they gain their name and possibly avoid the jaws of predators.

Upward-looking eyes are covered with a maze of incredibly tiny features called nanostructures that enhance their ability to sense wavelengths of light in the visual range. Downward-facing eyes that peer into the relative gloom below the surface lack these nanostructures. Separate nerve centers in the beetle’s tiny brain receive visual information from both pairs of eyes, integrate this information, and use it to hunt prey, find mates, and avoid predators. It is difficult for a binocular animal like me to even imagine what all of this must look like. Amazing!

The rapid, swirling movements of whirligigs are thought to help confound visually hunting predators. Whirligigs have yet another defense against their aquatic enemies, this one a nasty tasting chemical called gyrinidal produced by glands in their abdomen. When offered whirligig beetles as a snack, largemouth bass rejected them. Crazy swirly swimming, noxious chemical defenses, and four compound eyes, these are the special powers needed for whirligig beetles to survive at the interface of air and water.

Acknowledgements

Bug of the Week enjoyed “Secret Weapons” by Thomas Eisner, Maria Eisner, and Melody Siegler, and “Under- and over-water halves of Gyrinidae beetle eyes harbor different corneal nanocoatings providing adaptation to the water and air environments” by Artem Blagodatski, Michail Kryuchkov, Anton Sergeev, Andrey A. Klimov, Maxim R. Shcherbakov, Gennadiy A. Enin and Vladimir L. Katanaev, that provided the fascinating information for this episode.

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White bundles of fluffy wax are a sure sign of a woolly adelgid infestation on hemlocks.

Eastern hemlocks are beautiful native trees well suited for landscapes.

Eastern hemlock is a wonderful tree native to North America, found in the wild stretching from the shores of the Chesapeake to the Blue Ridge Mountains and beyond. In neighborhoods it graces landscapes as an evergreen specimen or screen along property lines. More than six decades ago, the hemlock woolly adelgid, a dastardly sucking insect akin to an aphid, appeared near Richmond, Virginia. It likely entered this country on infested nursery stock from Japan. For many years this pest made its presence known mostly in home landscapes and parks, where it often disfigured and sometimes killed hemlocks. As it spread to the Appalachian Mountains, it killed thousands of eastern hemlocks in the Shenandoah, Blue Ridge, and Smokey mountains. A recent study estimated government and household expenditures to control hemlock woolly adelgid and lost property values when hemlocks died exceed $214 million annually in the United States. From Maine to Georgia this pest threatens eastern hemlock in the north and its rarer cousin, the Carolina hemlock, in the south.

The hemlock woolly adelgid has killed thousands of eastern hemlocks throughout natural and managed landscapes in eastern North America.

This mini-monster spends most of the summer and early autumn hunkered down as an inconspicuous immature stage, called a nymph, on the bark of the hemlock near the base of needles. When the cold winds of winter blow in late October and November, the nymphs resume development and mature in mid-winter. Currently in my neighborhood this process is underway, with adelgids producing large amounts of white, woolly wax from which the woolly adelgid takes its name. The waxy cover provides protection for the adelgid and for eggs she will lay in the woolly sac in late winter. Between March and June, a second generation of adelgids will hatch out and mature, and then the cycle begins again with females producing the next batch of nymphs that will summer on hemlock twigs. Excepting the summer season of dormancy, developing nymphs and egg-laying females feed by inserting hypodermic-like mouthparts through the bark of twigs. The long, sucking mouthparts search along the tree’s vascular system and eventually find specialized tissues called parenchyma cells of the xylem rays. The mouthparts are inserted into parenchyma cells and the adelgid greedily robs the tree of its stored nutrients. Heavily infested trees decline in vigor, turn a sickly grayish – green color, lose their needles, and may die in five to ten years, if adelgids are not controlled.

What lies beneath the wax? Wax on reveals little, but wax off reveals wiggling legs and rows of wax-producing pores lining the underside of the bizarre looking immature adelgid.

We have painted a picture of the adelgid as a despicable pest very much accustomed to thriving in winter’s cold in many parts of the eastern United States. As the world warms, scientists fear the range of the adelgid will expand dramatically to many northern reaches in the United States and southern Canada. In these chilly lands, the adelgids’ hemlock hosts are currently protected by frigid winter temperatures lethal to the overwintering stages of the adelgid. As the world warms, this thermal refuge for hemlocks is in jeopardy. But there seems to be an upside related to the warming of our world with respect to the current geographic range of the hemlock woolly adelgid. Recently, scientists have discovered that in the southernmost lands invaded by the adelgid, the hemlock forests of Georgia, summer temperatures have become hot enough to significantly reduce the survival of the adelgid on imperiled hemlocks, particularly those at warmer low elevations. While a warmer world may open the door for the adelgid’s continued northward march, perhaps the same phenomenon will close the door to its persistence in the south. Only time will tell.

Acknowledgements

The following articles where consulted in preparation of this episode: “Economic impacts of non-native forest insects in the continental United States” by J. E. Aukema and colleagues, “Biology and Control of Hemlock Woolly Adelgid” by N.P. Havill, L. C. Vieira, and S. M. Salom, “Increases in summer temperatures decrease the survival of an invasive forest insect” by Angela M. Mech, Patrick C. Tobin, Robert O. Teskey, and J. Rusty Rhea, and Kamal J. K. Gandhi, and “Responses of insect pests, pathogens, and invasive plant species to climate change in the forests of northeastern North America: What can we predict?” by Jeffrey S. Dukes, Jennifer Pontius, David Orwig, Jeffrey R. Garnas, Vikki L. Rodgers, Nicholas Brazee, Barry Cooke, Kathleen A. Theoharides, Erik E. Stange, Robin Harrington, Joan Ehrenfeld, Jessica Gurevitch, Manuel Lerdau, Kristina Stinson, Robert Wick, and Matthew Ayres.

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Like psychedelic posters from the 60’s, rockin’ tropical scorpions glow beneath the beams of a blacklight.

One delightful adventure not to be missed is a nocturnal foray into the heart of a tropical rainforest. This escapade can produce memorable encounters with whip scorpions, large tarantulas, and giant katydids like those we met in previous episodes. During one such foray in Costa Rica, I was surprised to see a beautiful blue-green scorpion resting on the ground when a trail guide moved a fallen leaf and cast the beam of a blacklight near the path. Being a child of the 60’s, I was instinctively struck to understand what my blacklight posters shared with this stinging eight-legged rainforest predator. It turns out that blacklight posters contain compounds, phosphors, capable of capturing the high energy photons of UV light and releasing their energy in longer and less energetic forms of visible light, producing dazzling, glowing hues. Scorpion glow results when UV light is captured by two compounds, beta-carboline and 4-methyl-7-hydroxycoumarin, found in the scorpion’s exoskeleton. Once captured, UV’s energy is released in the form of eerie blue-green florescence.

A scorpion is revealed amongst leaves on the rainforest floor as it fluoresces bluish-green when illuminated by rays of a blacklight.

In a series of clever studies, Dr. Douglas Gaffin and his colleagues discovered that the scorpion’s entire body may act as a photoreceptor or universal “eye” used to detect different levels of light. Light in the UV range directed at scorpions produced bouts of rapid movement. These researchers suggested that the scorpion’s whole-body “eye” might help it move to places where light no longer illuminates its body, such as locations beneath vegetation where the searching eyes of larger predators were less likely to spot it. Whole-body photoreceptors might also be used by scorpions to detect the waning light levels of twilight, the signal to exit burrows and start their nocturnal hunt for prey.

Who’s that lurking in the corner of the bed frame? And is that another wedged in the crack above?

On another tropical adventure in the rainforests of Belize I had the good fortune to encounter scorpions in a somewhat different context. After a long day of feeding mosquitoes and avoiding crocodiles with a group of students on a study abroad, the prospects of enjoying a little shut-eye in the bunkhouse was most appealing. Unfortunately, one student climbed into his lower bunk bed and was surprised to see a rather impressive scorpion beneath the mattress of the upper bed just a few inches above his head. In Belize, the solitude of bedtime is often punctuated by colorful and enthusiastic expletives describing the creatures found in cabins. The exciting Slenderbrown scorpion, like the one encountered by our student, is a regular visitor to cabins and outhouses at night, and goes by many names including the Slenderbrown, Brown Bark Scorpion, or Alacran azul. In the wild, I have seen it beneath loose bark and under logs. This scorpion is found in Central and South America, the Caribbean, and southern Florida.

Scary pinchers, or pedipalps, are used to capture prey.

If this sting gets you, you will be sending out an SOS to the world.

Scorpions are not insects. They belong to another part of the arthropod clan called arachnids and are relatives of spiders and ticks. The scary pinchers on the front end of the scorpion are its pedipalps. They are used for grasping and dismembering insects and spiders that comprise most of the scorpion’s meals.

The business end of the scorpion is the sting, an enlarged segment at the end of the scorpion’s tail that contains a venom gland and a needle-like poker to deliver the poison. The sting is used to immobilize and kill prey and also as a means of defense against larger animals. When scurrying across a floor or ceiling, the scorpion’s sting is often curled up and over its back. Scorpions move surprisingly fast. The venom of the Slenderbrown scorpion carries a punch similar in pain to the sting of a honeybee or yellow jacket and is not generally life threatening. However, some relatives of the Slenderbrown scorpion, including those in the genus Tityus, are very dangerous and their venom can be fatal to humans. One courageous and somewhat impulsive student tested the potency of the Slenderbrown’s sting when she grabbed a scorpion lurking over her bunk and was stung. She summarily hurled said scorpion out the door of her cabin. Her assessment of the experience: “It only hurt a little and that thing was really annoying me”. You go girl!

Acknowledgements

Many thanks to Dr. Jeff Shultz for an enlightening discussion about scorpion glow. The fascinating article “Scorpion fluorescence and reaction to light” by Douglas D. Gaffin, Lloyd A. Bumm, Matthew S. Taylor, Nataliya V. Popokina, and Shivani Manna provided much background information for this episode. Thanks also to Matt Tabisz for wrangling the scorpion in this Bug of the Week.

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Wingless, flightless, non-feeding, winter-active, what a strange moth is this female fall cankerworm.

Flight-capable male fall cankerworms are often seen on mild winter nights resting on trees or near porch lights.

Last year was spectacular for moths and butterflies. We visited many beautiful butterflies including brush-foots and swallowtails, and several marvelous moths such as silk moths and webworms. One of the more curious members of the moth clan, fall cankerworm, made its presence known on a blustery day last week. This enigmatic creature defies several “norms” found in the rest of the moth coterie. As you know, most moths are winged creatures that frequent the skies on summer nights as they search for mates and suitable plants on which to lay their eggs. However, female fall cankerworms are wingless. They have forgone their ability to fly. Is this some unfortunate twist of fate or the curse of a malevolent sylvan fairy? Perhaps, but many entomologists believe that wingless cankerworm moths have found a clever way to leave behind more offspring. By shifting precious bodily resources from equipment needed for flight, such as wings and muscles to flap them, and redirecting these resources to the production of eggs, female cankerworms may be able to bring more little caterpillars into the world and enhance their lineage’s odds for survival.

High in the treetops fall cankerworms deposit eggs on the bark of branches and twigs.

Regardless of the reason that underlies the mystery of the wingless moth, they are a wonder to see. Beginning in late autumn, adult fall cankerworms emerge from pupal cases in the soil. Females move from the soil and climb vertical structures such as trees and buildings. Shortly after sunset, on milder winter nights, female moths release a chemical signal called a sex pheromone that attracts male moths. Fall cankerworm males have functional wings and are good fliers. Each male tracks the pheromone to its source and the chilly couples mate. After this interlude, females climb high into the tree and place their eggs on the bark of small branches and twigs. Females do not live to see their offspring. Unlike other species of moths that have tubular mouthparts used to sip nectar, the female fall cankerworm lacks functional mouthparts. She cannot feed and shortly after depositing her eggs she dies.

Shredded leaves left behind by hungry caterpillars give these pests their common moniker, cankerworm.

The larvae of fall cankerworms hatch early in the spring soon after the buds of trees open and young leaves appear. Caterpillars of fall cankerworms and other members of their clan are also known as inchworms. They have multiple legs on their front and rear ends. By alternating their grasp between front and rear legs and bending their body upward into a loop, they move along twigs and leaves as if measuring the world an eighth of an inch at a time. The name cankerworm derives from the shredded, cankered mess caterpillars make as they consume foliage of trees. Their larvae reach phenomenal numbers in some locations and years, and may devastate many shade trees such as oaks, maples, elms, and lindens. We learned more about the ravages caused by this native pest in a previous episode of Bug of the Week. In addition to the fall cankerworm, other members of their clan such as spring cankerworm and linden looper, are active in the winter and have flightless females. A close relative of the fall cankerworm called the winter moth has recently appeared in cities and suburbs in New England, where it has become a perennial pest wreaking havoc on several species of shade trees in those areas.

On a bright winter day an adult fall cankerworm tries to ignore the annoying thumb of a bug geek. Can you guess why cankerworm caterpillars go by the name inchworms?

On a bright but chilly winter day visit a maple, elm, or oak and try to catch a glimpse of these strange ladies as they escape their earthly confines and slowly ascend trees in search of suitable repositories for their eggs. 

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