Upside and downside of a warming world for the despoiler of hemlocks: Hemlock woolly adelgid, Adelges tsugae

 

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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A cluster of female (larger ant) and male (smaller ant) smaller citronella ants seem ready to set forth to found new colonies on a warm afternoon in December.

 

The appearance of winged citronella ants emerging from beneath my front sidewalk was a welcome surprise in this somewhat dismal season for observing insects and their kin outdoors in the DMV.  Swarms of winged, a.k.a. alate, ants are often seen emerging from the earth to mate and found new colonies in warmer months in temperate regions. However, ants in the genus Lasius have been observed emerging from the earth in Maryland as late as November, so maybe December 27 is not such an odd date to witness this remarkable event. While not an ant expert, these little rascals looked like the smaller yellow ant, Lasius claviger, to me.

What a holiday surprise! Watch as large winged
females, smaller winged males, and wingless yellow worker citronella ants emerge from the earth and swarm on my front sidewalk.

When disturbed, bright yellow worker ants release alarm pheromones to recruit nest-mates to assist in defending the colony.

Lasius ants go by many colorful names including citronella ant, yellow ant, and lemon ant. The lemony scent we know as citronella owes to a compound found in many plants including lemon, lemon grass, and several species of eucalyptus. Special glands near the jaws of Lasius ants produce aromatic lemon scented citronellal. When threatened by an intruder, citronella ants send out an alarm by releasing citronellal. This pheromone brings nest mates running to assist in the defense of the colony. In addition to the well-known insect repellency of citronella, citronella ants have one more chemical trick up their sleeve, or should we say, in their rear end. Glands near the tip of the abdomen produce irritating formic acid. Formic acid contacting the eyes or face of an attacking predator serves as a powerful deterrent. This type of chemical warfare is an important strategy used by many species of ants.

Large yellow ants will sometimes swarm inside homes much to the dismay of unsuspecting homeowners.

In a previous episode we met large citronella ants that sometimes making a surprising appearance when their subterranean colony vents inside a home. Fortunately, Lasius ants are not wood destroyers like their cousins the carpenter ants. In addition to hunting soft-bodied prey, Lasius are herders. Yes, that’s right, they actually shepherd root feeding aphids, moving them from the roots of one plant to another to optimize the production of nutrient rich honeydew excreted by the aphids. As you may know, honeydew is an important and much sought-after food for many species of predatory and parasitic insects.

Citronella ants are relatively common in urban landscapes. I frequently encounter them while working in my flower beds and garden. You will too. Just take a moment to notice the pleasant fragrance of lemon as you turn the soil and then have a close look in the soil for these tiny and fascinating chemical warriors. 

Acknowledgements

The wonderful references “The Ants” by Bert Hölldobler and Ed Wilson, and “Secret Weapons” by Tom Eisner, Maria Eisner, and Melody Singer were used in preparation of this episode. Jeff and Linda shared the swarm of large yellow ants that emerged inside their home. Thanks also to Dr. Paula Shrewsbury for assistance with photography.

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Among frosty fronds, a scorpionfly gazes on a frozen landscape. Does she await her mate or ponder her next bite of moss?

 

Last week parts of the east coast were treated to their first real taste of wintry weather in the form of bone chilling temperatures, freezing rain, and snow. As we wind-down what has been a spectacular year for many of our six-legged friends, is it time to bid farewell to insects outdoors? Well, not exactly. You see, many tiny and not so tiny arthropods have adapted to a hibernal lifestyle and can be visited even on days when mammals are snoozing snugly in a cave or curled up in front of a fire sipping hot chocolate and reading a book. This week we visit one such character enjoying its day in the winter sun.  

Neither snow, nor ice, nor freezing temperatures can stop a female scorpionfly from scaling a miniature glacier to reach a scrumptious patch of moss. 

Carol Of The Bells by Audionautix is licensed under a
Creative Commons Attribution license (https://creativecommons.org/licenses/by/4.0/)
Artist: http://audionautix.com/

In a patch of moss near the banks of an icy stream, one of my colleagues discovered snow scorpionflies, one of the rarest insects we will meet in Bug of the Week. Snow scorpionflies are not scorpions, nor are they flies. They belong to a small order of insects known as Mecoptera. The “scorpion” moniker stems from the fact that some species of male scorpion flies have unusually large and upward curving genitalia that resemble the stinger of a scorpion. The “fly” part of the name comes from the fact that many species of Mecoptera have wings and can, well, fly. The tiny snow scorpionflies featured in this bug of the week do, in fact, lack functional wings, and cannot fly. Most species of snow scorpionflies are boreal and live in chilly places such as Alaska and Canada or occupy high elevations in mountains. They are active during the colder months of the year and can be seen with some regularity hopping about even on very frosty days. However, in Maryland snow scorpionflies can be found in the dead of winter on snow, ice, or on mosses and liverworts that serve as food for both adults and their larvae.

Chilly feet don’t cool the romance between winter-loving scorpionflies.

In one of the more curious mating rituals in the insect world, the male scorpionfly couples with the female, grasps her, and places her on his back for a nuptial ride. One has to wonder if this piggyback routine is just for fun or more likely a way to limit access to her by interloping suitors. If you hope to glimpse these fascinating creatures, dress warmly and bring along your magnifying glass. Snow scorpionflies are tiny insects, usually five or fewer millimeters in length. In a strange and still mysterious twist of evolution, snow scorpionflies are believed to be the ancient relatives of one of our more well known and itchy insect friends, the fleas.  

 

Bug of the Week wishes all of you a Happy Holiday and a joyous New Year.

 

 Acknowledgements

 Many thanks to Chris Taylor, Tom Pike, and Jeff Shultz for sharing his snow scorpionflies for this Bug of the Week. The wonderful reference “Scorpionflies, hangingflies, and other Mecoptera” by G. W. Byers was consulted in preparation of this episode.

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Rhinoceros beetles like this male Hercules beetle use their impressive horns to battle each other for access to mates.

 

Fully grown grubs of the Hercules beetle are prime tucker for bears, raccoons, and other wildlife.

In Roman mythology, Hercules was a hero of remarkable strength and courage renowned for performing amazing feats such as slaying the 9-headed water beast called the Lernaean Hydra, exterminating man-eating birds, and cleaning a mighty big stable in a single day by rerouting two rivers to flush away the filth. Sometime ago one of our former students happened across several extraordinarily large beetle grubs, named for this mythological hero, in a hollow of a decaying cherry tree. Nearby, a rambunctious male Hercules beetle did his best to win the affections of an adorable female beetle, but unfortunately to no avail.

Clearly this lass wants no part of the amorous male. The hapless suitor can only watch as she disappears beneath the mulch, the ultimate rejection!

Here in the DMV, native male and female Hercules beetles, a type of rhinoceros beetle, can be held in one hand.

The Hercules beetle is the largest beetle found in eastern North America. Like its namesake, this beetle is crazy strong. When placed in a terrarium with a tightly fitting lid on my kitchen counter, the male Hercules beetle easily lifted the lid, climbed out, and went for a stroll around my home. Our local Hercules beetle belongs to a family called the Scarabaeidae, which includes pests such as the Japanese beetle and Oriental beetle we met in previous episodes. By virtue of the exceptionally long horns found on the males, these scarabs are also fondly called rhinoceros beetles. Some male rhinoceros beetles in the tropics have exceptionally long horns, used to wage war with other males as they vie for the right to mate. Battles consist of males challenging each other with a series of squeaking sounds. This may be followed by a tussle involving dueling with horns. The winner usually gets the gal and the loser retreats, sometimes with more than his pride wounded.

But in Belize, it takes two hands to hold magnificent female and male rhinoceros beetles.

In the wild, the main food of adult beetles is the sap of trees and fruit. Beetles create a sap-flow by scraping away tender bark of the tree. In captivity, adult Hercules beetles eat fresh and rotting fruit including apples, oranges, cherries, and bananas. Adult beetles live several months and lay rather large eggs in rotting wood of hollow or fallen trees. Larvae may require 12 to 18 months to complete development, attaining a size of roughly two inches in length. The larvae, called grubs, consume decomposing wood and organic matter. They change to pupae from which emerge new adults.

These guys make interesting pets and are fairly easy to rear. The website listed below contains instructions for the culture and care of these creatures. Unfortunately, Hercules beetles are attracted to lights and they sometimes appear at porch lamps or in illuminated parking lots, where they are eaten by predators or killed by humans. Although these very large beetles appear scary, they are harmless to humans. If you see one or encounter the grubs, enjoy them and return them to the wild unharmed. They are important recyclers of nutrients locked-up in wood and one of Mother Nature’s most fantastic creations.

After being exposed by a meddlesome hand, a bashful Hercules beetle grub dives into the substrate to avoid the inquisitive lens of the paparazzi. Grub entering soil filmed at seven times actual speed.

Acknowledgements

Special thanks to Ellery and Erik for sharing their family of Hercules beetles with Bug of the Week. To learn more about the biology and ecology of rhinoceros beetles and how you can raise them, please visit the following website: https://www.uky.edu/Ag/CritterFiles/casefile/insects/beetles/hercules/hercules.htm#ecology

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Darkling beetles huddle beneath the bark of a log to escape winter’s chill.

With the return of chilly wintery weather, it’s time to split a few logs for the fireplace. As you wield your axe or maul, take a few moments to peel back the loose bark on some logs. You might be surprised by what you find. If your firewood is not too old and punky, just beneath the bark you may find serpentine galleries that wend their way along the surface of the hard wood. Examine the inner surface of the bark and you will see the mirror image of this trail. Galleries like these are often created by beetle larvae called roundheaded borers and many of my maple logs were chuck full of these wood-eaters. After completing development beneath the bark, they chew a round hole to the outside of the log and emerge as a longhorned beetle, so named for the remarkable length of their antennae.

It’s easy to see how Asian Longhorned Beetle got its name. Just look at those antennae.

 Many species of roundheaded borers like the ones tunneling through my maple logs prefer to eat the tissues of dying or dead trees. Some like the dreaded Asian Longhorned Beetle attack living trees with a preference for those under stress. This beetle is responsible for the death of tens of thousands of trees in New York, Chicago, New Jersey, Massachusetts, and Ohio since its introduction to the United States in the 1990’s. Roundheaded borers that eat wood have powerful jaws to chew their way through hard plant tissues. We met other longhorned beetles in a previous episode as they dined on nectar and pollen. If you bring firewood into your home and store it for an extended time before you use it, you may be treated to the emergence of several wonderful longhorned beetles, maybe just in time for the Holidays!

Looking like a sleepy Jabba the Hutt beneath the bark of my firewood, a roundedheaded borer wriggles in its gallery. After completing development, it becomes an adult longhorned beetle, so named for its exceptionally long antennae similar to those of the stunning locust borer.

 As I peeled back the lose bark of a second maple log, I discovered a bevy of darkling beetles. Darkling beetles spend the winter in a frigid scrum beneath the bark of trees awaiting the warmth of spring to resume their activities. Most darkling beetles feed on plant material of some sort – living or decaying. Not far from where the adult darkling beetles huddled, several darkling beetle larvae moved at a glacial pace through the decaying wood beneath the bark. Like their roomies, the roundheaded borers, darkling beetle larvae complete their development when the warmth of spring returns.

Just under the bark, an Emerald Ash Borer larva has almost completed its development. A frass filled gallery marks its progress through the wood.

In addition to maple logs, I have a great store of ash firewood thanks to the nefarious Emerald Ash Borer that has killed more than a million ash trees since its introduction to North America some two decades ago. And as I split some of the ash logs, what to my wondering eyes should appear, but an almost fully developed larva of the Emerald Ash Borer. This little rascal will complete its development under the bark next spring and emerge in May as a gorgeous adult beetle known as a metallic wood boring beetle.

Classic D-shaped exit hole of a flatheaded borer, in this case the Emerald Ash Borer.

The Emerald Ash Borer larva is called a flatheaded borer. It too makes sinuous galleries beneath the bark, but upon emerging from the tree the adult leaves behind a tell-tale exit hole in the shape of the letter “D.” Get it, D has a flat side and so does the hole made by a flatheaded borer. Entomologists are pretty clever, eh?

A beautiful but deadly Emerald Ash Borer battles a giant finger before flying away. It is one of many metallic wood boring beetles that attack and kill trees.

So, during this most wonderful time of the year, on a wintry night when you are sitting in front of the fireplace singing the songs you love to sing and watching the chestnuts pop, pop, pop, listen carefully: those might not be chestnuts popping.

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Does the wide orange band portend a mild winter ahead?

 

I usually think of caterpillars as rather delicate creatures and sometimes wonder how they survive bone chilling cold in places like Maryland where polar vortices sometimes visit. A fascinating study by Jack Layne and his colleagues revealed that woolly bear caterpillars survive winter’s cold through a process called supercooling. As temperatures drop in autumn and early winter, woolly bears and many other species of insects produce cryoprotectants, antifreeze-like compounds including glycerol and sorbitol, that prevent the formation of lethal ice crystals in their bodies. This brew of Mother Nature’s antifreeze allows caterpillars to survive even when ambient temperatures dip well below freezing.

The banded woolly bear turns into the pretty Isabella tiger moth.

One of the most interesting and commonly encountered caterpillars of late autumn is the banded woolly bear. This dashing caterpillar began life in spring when it hatched from an egg laid by its mother, the Isabella tiger moth. Eggs deposited on nutritious vegetation, maybe a dandelion or an aster, hatch into leaf-munching caterpillars that feed during spring, summer and autumn on a broad range of plants. However, the caterpillar fails to transition to a pupa during the growing season. The partially grown woolly bear passes the winter, or, in bug-geek-speak “overwinters”, as a larva. In spring with the return of warm temperatures and arrival of fresh leaves, it feeds a short while before spinning a cocoon and completing the transformation to an adult moth. The pretty orange moth is rather unremarkable as tiger moths go, but the caterpillar certainly catches one’s attention with its alternating bands of black and orange.

A popular folktale has it that the woolly bear can forecast the harshness of an approaching winter. A wide orange or brown band in the middle bordered by black bands at head and tail indicates that a mild winter is at hand. Conversely, a narrow band of brown or orange means that a long, severe winter is on the way. A noted entomologist from the American Museum in New York City, Dr. C. H. Curran, tested this idea by collecting woolly bear caterpillars from nearby Bear Mountain Park each year between 1948 and 1956. He used band-width observations to forecast the severity of the upcoming winter and his observations gained notoriety when published in the New York Herald Tribune. Several other entomological experts around the country have used various clues garnered from the woolly bear to predict the winter weather. Claims of 70-80% accuracy are not uncommon.

A banded woolly bear races across my driveway to find winter refuge.

A bit earlier in the season, I discovered a tiger moth caterpillar dressed only in orange and was delighted at the prospect of an incredibly mild winter. I imagined paltry fuel bills and fantasized about how I would spend the extra money. Unfortunately, a little research revealed this pretty orange caterpillar to be the saltmarsh caterpillar, Estigmene acrea. The saltmarsh caterpillar lacks black bands and, apparently, any ability to predict weather.

The gorgeous and very hairy saltmarsh caterpillar fattens up on weeds in preparation for its wintry respite.

A bit later in the season a viewer sent me an image of a solidly black tiger moth caterpillar, one completely devoid of the hopeful orange band and obviously the herald of a dreadfully long and bitterly cold winter.

The adult leopard moth, mother of the giant woolly bear, is a thing of beauty with black patterned white wings.

 

But once again, a little digging proved this to be not a banded woolly bear, but the larva of the giant leopard moth known as the giant woolly bear, a.k.a. black woolly bear. Like its cousins the banded woolly bear and saltmarsh caterpillars, caterpillars of the giant leopard moth eat a wide variety of woody and herbaceous plants, such as dandelion, plantain, violets, cherry, and honeysuckle, to name a few. Its magnificent coat of stout, black hairs is a formidable defense.

 

When threatened, the giant woolly bear caterpillar presents a phalanx of stout spines punctuated by crimson rings between body segments – a strong warning to would-be predators and bug geeks.

When disturbed by a predator or bug geek, the caterpillar curls into a tight round ball of prickly black spines. What an unappetizing meal for a would-be predator! The adult is a fantastic large moth with a white coat adorned with black circles, bars, and dots. In the waning days of autumn, enjoy these caterpillars as they dash about and please leave them undisturbed if you discover them beneath a pile of leaves or under the loose bark of a tree where they are chillin’ out for winter.  

Acknowledgements

Bug of the Week thanks Sheri, Finn, and Iggy for inspiring this episode and Karin Burghardt for providing images and identifying featured caterpillars. David Wagner’s remarkable book, “Caterpillars of Eastern North America”, was used to prepare this story, as was the interesting article “Cold Hardiness of the Woolly Bear Caterpillar (Pyrrharctia isabella Lepidoptera: arctiidae)” by Jack R. Layne Jr, Christine L. Edgar, and Rebecca E. Medwith.

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What has bright vermilion eyes, two wings, and an extraordinary fondness for over-ripe fruit?

With Halloween a quickly fading memory, I visited my Jack O’ Lanterns one last time before their final journey to the compost heap. While lamenting the passing of my pumpkins, I was delighted to see dozens of tiny winged workers fully engaged in the decomposition process. Flies are important recyclers of dead plants and animals. They provide a vital ecological service by unlocking nutrients tied up in complex molecules and returning them to food webs. In this episode we meet the fruit fly, a master transformer of plant material. The common name fruit fly is often used to describe small ( ~ 3 mm) flies with bright red eyes in the family Drosophilidae (a.k.a. vinegar or pumice flies). Larger flies sporting spotted or banded wings in the family Tephritidae also go by the name fruit fly by virtue of their appetite for fruit and other parts of plants. Details of the former will be investigated today and strange dealings of the latter await another episode.

In autumn I regularly receive questions about hordes of tiny fruit flies buzzing around fruit bowls, kitchen sinks, and counter tops. They seem to appear from nowhere and lend credence to Aristotle’s notion that living organisms like tiny flies can originate spontaneously from non-living or putrefying things. Now famous experiments by Francesco Redi and Lazzaro Spallanzani pretty much disproved Aristotle’s theory of spontaneous generation, but the appearance of hordes of tiny flies remains vexing even for bug geeks.

To help untangle this mystery, consider the change of seasons.  Autumn in many parts of the country is characterized by damp cool weather by virtue of incessant weekly showers. These moist conditions are nearly ideal for decomposing tons of leaves, fruits, and other vegetable matter, the accumulated bounty of Mother Nature’s efforts during spring, summer, and autumn. This week of Thanksgiving my compost pile is a writhing mass of invertebrates intent on converting vegetable protein into animal biomass as quickly as possible. On warm days a cloud of fruit flies hovers over my compost pile and some of these winged raiders undoubtedly infiltrate my home when the door opens. Like many kitchens, mine is home to a bowl of fruit that occasionally contains one item gone a little squidgy. Yeasty odors of acetic acid and ethanol emanating from an over-ripe banana serve as powerful attractants for fruit flies. After arriving at the banana, the female fruit fly deposits eggs. Each gal lays roughly 500 eggs during the course of her life time. Small translucent larvae hatch from the eggs. They glide through the overripe fruit slurping-up nutritious fermenting fluids as they develop and grow. When ambient temperatures are warm, fruit flies can complete a generation in less than two weeks. With their capacity for reproduction, populations around the fruit bowl can explode seemingly overnight.

While adult fruit flies feed on the surface of my pumpkins, taking special care to groom antennae and legs, their offspring are busy dining inside. Watch how the larva uses darkly colored mouth hooks to propel itself forward by grasping the substrate and pulling itself along. Ah, but once it finds just the right juicy spot it stops and slurps the nutritious tissues of decomposing pumpkin flesh.  

Fruit flies can also enter your home as stowaways when you purchase overripe fruits or vegetables from the market. These goods may arrive preloaded with a complement of eggs or tiny larvae. To reduce chances of bringing home an infestation, inspect your produce carefully and wash fruits and vegetables. If fruit is unrefrigerated and displayed in a bowl, check it out regularly and toss over-the-hill items before they generate flies. Fruit flies can also breed in sink or floor drains, garbage pails, or recycling containers in homes, restaurants, and offices where decomposing organic material accumulates. Inspect these areas regularly, clean up spills, and disinfect surfaces.

Yeasty odors of fermenting fruit and wine vinegar lure scores of fruit flies and one fungus gnat to their death.

Fruit flies are more than just an indoor nuisance. Several species are important pests of agricultural crops. The spotted wing drosophila, Drosophila suzuki, first detected in the US in 2008 in California, has now spread from coast to coast and border to border. It is a major pest of strawberries, blueberries, raspberries, black berries, and cherries. Crop losses in the United States alone are estimated to exceed hundreds of millions of dollars annually.  For the cloud of fruit flies wafting around your home, consider building a vinegar trap to catch and kill these noisome rascals.  Traps can be purchased commercially and several trap designs are available on the internet. My vinegar trap consists of an 8 oz clear plastic tumbler filled with 4 oz of wine vinegar and a few drops of dish detergent. Within 24 hours of placing the trap on the counter, more than 100 fruit flies were lured to their death. Stealing a line from Robert Armstrong of King Kong fame (RKO, 1933) “Oh no, it wasn’t the banana that killed the beast. It was the fragrant odor of yeast.”

Hope you enjoy your pumpkin pie this Thanksgiving. Have a happy one!

References

We thank Liz and her buggy bananas for providing the inspiration for this episode. The interesting references “Trapping spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), with combinations of vinegar and wine, and acetic acid and ethanol” by P. J. Landolt, T. Adams, and H. Rogg,  “Spotted Wing Drosophila: Potential Economic Impact of Newly Established Pest by M. P. Bolda, R. Goodhue, and F.  Zalom, and “Flies, gnats, and midges” by W. A. Kolbe in “The Handbook of Pest Control” were used in preparing this Bug of the Week.

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Strangely delicate and beautiful, but a bit creepy at the same time, house centipedes are common home invaders around the globe.

A couple of weeks ago, a Bug of the Week viewer messaged me about a fast moving, many-legged creature darting across the floor. Early one morning last week I had a similar surprise when I stepped into the shower and was greeted by a magnificent house centipede scuttling around the tub. In previous episodes of Bug of the Week we met other home invaders that somehow wind up in the bathtub, like camel crickets and wolf spiders. The house centipede is yet another creature that evolved in a foreign land and now claims the US as one of its homes. Originally found in the Mediterranean region, it now occupies most of Europe, parts of Asia and Africa, and lands in Central and South America, as well as North America.

‘Centipede’ is a bit of a misnomer. They don’t really have 100 legs, but more like about 30.

Steve Jacobs, an extension specialist at Penn State, related a fascinating story about the house centipede first published by one of the forefathers of entomology in the US, C. L. Marlatt, in 1902. Regarding the house centipede, Marlatt said, “It may often be seen darting across floors with very great speed, occasionally stopping suddenly and remaining absolutely motionless, presently to resume its rapid movements, often darting directly at inmates of the house, particularly women, evidently with a desire to conceal itself beneath their dresses, and thus creating much consternation.”  Ladies, nowadays it’s a good thing workout leggings are in vogue.

In the natural world, house centipedes thrive in moist, cool places and can be discovered on the soil beneath rocks, logs, and fallen leaves. Once inside a home they gravitate to similar locations: man-caves in the basement, laundry rooms, and bathrooms. So, how do they wind up in the bathtub? Well, contrary to popular belief they do not swim up through the drain. This trick is mostly practiced by mammals like rats, able to hold their breath long enough to swim through the water-filled trap in a drain pipe. Centipedes and other creatures found in a tub usually were seeking a tasty insect or spider for a midnight snack on the rim of the tub, slid into the porcelain vessel, and could not scale the slippery walls to escape. Unlike their other many-legged relatives millipedes, that eat vegetation, centipedes are hunters and eat meat. You may recall the stone centipede we met in a previous episode and remember its powerful poison claw that came with the warning of “do not handle” lest you risk a nasty venomous bite. Well, the house centipede is also equipped with a similar, much smaller appendage but bites are rare and, according to several accounts, quite mild.

What a way to start the day – a centipede in the bathtub!

If you encounter a centipede in the tub, please avoid the urge to flush it down the toilet. This is a needless waste of water. Here’s what I do. After discovering a house centipede in the tub, I capture it in a water glass, transport to the backyard, and release it so it can hunt soil-inhabiting garden pests – a win-win for everyone except maybe the garden pests.

Acknowledgements

Bug of the Week thanks an anonymous viewer for inspiring this episode. “House Centipede” by Steve Jacobs provided the technical information. Please check out his great fact sheet at this site:  https://ento.psu.edu/extension/factsheets/pdf/HouseCentipedes2.pdf

Bug in the Bathtub? first appeared on Bug of the Week