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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

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A fantastic tropical flag-footed bug shows off his remaining hind leg.

Leaffooted bugs here in the DMV sport impressive flags on their hind legs.

Last week we met leaffooted bugs being attacked by parasitic tachinid flies. One of the featured creatures in this episode was a five-legged bug limping along in a feeble attempt to escape a nosy camera. Two questions surfaced regarding the five-legged bug in last week’s episode. First, what in the world are those fantastic leaf-like structures on the hind legs for anyway? Second, how did the unfortunate bug lose its leg in the first place? 

Dropping a hind leg on the bathroom floor while avoiding capture was enough to make the paparazzi stop to snap a picture.

This is not the first time we’ve met an insect missing a hind leg. Some of you may recall the episode entitled “Five-legged cricket in the bathtub” where we discovered that quite a few animals may discard an appendage, often a leg or a tail, when attacked by a predator. The strange behavior of discarding an appendage is not uncommon for many insects such as crickets, walking sticks, and yes, leaffooted bugs. A special muscle allows a leg or antenna to snap off at the insect’s will under the right circumstances. This phenomenon, known as autotomy, allows the insect to lose a leg and save its life by distracting a hungry predator. When the predator stops to examine or eat the severed limb, the bug makes its getaway. In some cases, the insect regenerates the missing part.

What message does the flag on the hind tibia of Diactor convey to a would-be predator?

In addition to insects, reptiles and mammals use this clever ploy. Some male relatives of the leaffooted bugs we visit today have powerful, enlarged hind legs used to battle other males for territories and access to females. Autotomy in these species comes with a cost to successful reproduction. Apparently gimpy guys are less likely to hold territories and win affections of desirable female bugs. The greatly expanded and highly apparent hind legs of Leptoglossus and the beautiful tropical flag-footed bug, Diactor, likely serve another purpose. One look at the amazing hind leg of the Diactor is certainly enough to attract the attention not only of entomologists but also the eyes of would-be predators. By directing a predator’s attack away from vital organs and body parts, these bugs may lose a leg and prevent the loss of a much more vital body part. For leaffooted bugs, crickets, and many other insects, losing a leg is much better than losing one’s life.  

Five legs propel a leaffooted bug along a railing; seem to suit a hungry field cricket just fine; and help a camel cricket hop, sort of, away from the guy with a camera.

As for how the unfortunate bug lost its leg, it was not inclined to share that information with us, focusing instead on the message that at least it got away.

Acknowledgements

The fascinating articles “Coreidae (Insecta: Hemiptera) Limb Loss and Autotomy” by Zachary Emberts, M. St. Mary, and Christine W. Miller, and “Combat and territorial defense of Acanthocphala femorata (Hemiptera: Coreidae)” by P. L. Mitchell were used as references for this episode.

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The female leaffooted bug enjoys a tasty corn snack while engaged with her mate.

As summer turns to fall, many insects with gradual metamorphosis, those with nymphs rather than larvae as juveniles, become adults and are more easily seen as the larger adults. This spawns a spate of requests from curious citizens to answer the question “what’s this bug?” In previous autumn episodes we met ferocious wheel bugs, deadly orange assassin bugs, and spooky milkweed bugs. This week we continue our sojourn into the realm true bugs, insects in the order Hemiptera, and learn the aromatically romantic ways of leaffooted bugs.  

How do I get around this giant hand that keeps following me? And this guy with a camera, what’s up with that? (Note the eggs of a parasitic tachinid fly deposited in the back of the adult bug; death is just around the corner).

A gaggle of leaf-footed bug nymphs dines on my pumpkin vine.

On a past visit to a cornfield, in addition to bevies of brown marmorated stink bugs, I notice legions of leaffooted bugs probing kernels of corn directly at the tips of the ears or through the tough cover of the husk. Named for the leaf-like expansion of their hind legs, leaffooted bugs belong to a guild of suckers that insert their hypodermic-like mouthparts into tender plant tissue. After injecting saliva laced with digestive enzymes, they withdraw nutritious fluids from the unfortunate plant. Both the bright red and black immature stages called nymphs and the winged adults feed in this remarkable manner. In addition to sucking the life from corn, the catholic diet of leaffooted bugs includes crops such as cotton, squash, and tomatoes, trees such as oaks and maples, conifers, vines, and shrubs with representatives from fifteen families of plants.  

Apparently a stickler for detail, the mother leaffooted bug neatly lays her eggs in very straight rows.

Adult leaffooted bugs live for several months and dine on many plants, but their reproduction occurs only in the presence of reproductive structures such as fruits on their host. Eggs of leaffooted bugs are curious contraptions resembling tiny barrels, tipped on their sides, aligned in a neat row. One can only wonder about the strangely linear thinking used by the bug as she neatly arranges her brood on the surface of a leaf. A circular bunghole on the side of each barrel provides the tiny nymph inside with an escape hatch once its development is complete.  

Uh oh, a doomed leaffooted bug has been visited by a tachinid fly. Larvae that hatch from eggs on its thorax will bore into the bug, consume its internal organs, and seal its fate.

Like brown marmorated stink bugs we met before, leaffooted bugs release nasty scents to ward off attacks by hungry predators. However, male members of the leaffooted clan have one more aromatic trick up their sleeve. A small gland in their abdomen produces aromatic compounds with the delightful scents of cherries, vanilla, cinnamon, or roses depending on the species of the bug. Each bug has a unique blend of these compounds, known as pheromones, that allows the fair member of the species to locate and accept an appropriate mate.  But in this game of olfactory romance, danger awaits. A clan of parasitic flies called tachinids uses several cues, including the pheromones of true bugs, to track their victims. Upon sensing the pheromone, they follow the trail to its source and deposit eggs on the exoskeleton of the bug. Eggs hatch and tiny maggots drill through the exoskeleton and enter the soft tissues inside the bug. Here they will feed and develop, eventually leading to the bug’s demise. So, in the realm of romance for the leaffooted bug, beauty truly is only skin deep. It’s how you smell that really counts. But does the peril of death sometimes accompany the fragrance of attraction? Maybe only male leaffooted bugs know for sure.   

 Acknowledgements

Bug of the Week thanks Jeff Aldrich for an interesting discussion that was the inspiration for this episode. The fascinating articles“Host Plants of Leptoglossus oppositus (Say) (Hemiptera: Coreidae)” by Paula Mitchell and Al Wheeler, “Bug pheromones (Hemiptera, Heteroptera) and tachinid fly host-finding” by J. R. Aldrich, A. Khrimian, A. Zhang, and P.W. Shearer, and “Species-specific natural products of adult male leaf-footed bugs (Hemiptera: Heteroptera)” by J. R. Aldrich, M. S. Blum and H. M. Fales were used in preparation of this story.

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Striking contrasts of orange body and black spines may serve as a warning to predators to avoid making a meal of Gulf fritillary caterpillars.

This week Bug of the Week finds itself in the tidewater of Virginia and on the sunny shores of South Carolina, where brilliant members of the aster clan carpet the sands just leeward of the dunes. Here in the waning days of autumn a beautiful butterfly dressed in orange and black sips nectar in preparation for its journey to frost-free zones along the Gulf of Mexico, while others find romance along a footpath in a garden. The Gulf fritillary is a broad ranging species taking up permanent residence from Argentina to the southern United States. During summer, peregrinations take it as far north as San Francisco on the west coast and New Jersey on the east coast, but in autumn this vagabond travels south to the warm climes of the Floridian peninsula to spend the winter.  

Flowers of the passion vine are among the most magnificent in the plant world.

 Like other members of the longwing butterfly clan, larvae of this orange and black beauty consume leaves of passion fruit vine. The blossom of the passion fruit vine is one of the most gorgeous in the angiosperm world. Exotic flavors of the passion fruit are used around the world adding zest to ice cream, cheesecake, and mixed drinks. Passion fruit is rich in vitamin C and lycopene and consuming this delicacy is said to sooth a queasy stomach, according to Andean lore. As a group, passion fruit plants are protected from most leaf-munching caterpillars and other vegan insects by a veritable witch’s brew of highly toxic chemicals including alkaloids, a family of toxins that includes strychnine and nicotine, and cyanogenic glycosides, chemicals that release cyanide upon entering the digestive tract of a caterpillar or human.

The gorgeous Gulf fritillary butterfly harbors a couple of unpleasant surprises for any would-be predator.

However, the Gulf fritillary and other members of its clan, including the zebra longwing we met in a previous episode, turned the tables on passion fruit plants, bypassing the noxious defenses and feasting with impunity on their leaves. Some species of longwings sequester cyanogenic glycosides from their food and others manufacture these compounds on their own. presumably for defense. The striking orange and black coloration of the Gulf fritillary warns vertebrate predators not to mess with this beauty. In addition to any plant derived defenses, the gorgeous Gulf fritillary has one more bit of chemical trickery to help keep predators at bay. Glands on the abdomen produce and release a concoction of complex esters when the adult butterfly is disturbed. This stinky defensive fluid dissuades predators such as birds from making a meal of these dazzling butterflies.

Like its cousin the Gulf fritillary, a zebra longwing caterpillar consumes large quantities of passion vine leaves each day.

But the beautiful Gulf fritillary is not all about noxious chemicals and defense. Oh no, in the Norfolk Botanical Garden some Halloween romance was literally afoot, where a mating pair of butterflies engaged in a quixotic duet along a footpath. Many male butterflies, including Gulf fritillaries, have a clever trick for winning the affections of would-be mates. At the tip of his abdomen the male Gulf fritillary has small bristles called hair pencils. The male uses his hair pencils to distribute aphrodisiac pheromones on the antennae of a potential mate. Courtship pheromones are often released by the male over the female while both are in flight. These pheromones calm the female’s innate escape response, and upon landing the male may hover over the female dusting her with more pheromones. The resulting romantic swoon induced by the pheromone allows the male to approach his mate and, well, shall we say, fulfill the biological imperative of procreation.

Asters provide a rich source of carbohydrates to fuel the Gulf fritillary’s autumn migration to frost-free zones in the Deep South along the Gulf of Mexico. Along a foot path a male Gulf fritillary releases aphrodisiac pheromones over the antennae of a potential mate. Will this clever behavioral trick result in a Halloween treat?

 Beautiful, dangerous, romantic; what could be more perfect for an insect dressed in orange and black for this festive autumn season? Hope you have a Happy Halloween!     

Acknowledgements

 References used in the preparation of this Bug of the Week include ‘Caterpillars of Eastern North America’ by David L. Wagner; ‘Coevolution of Animals and Plants’ by Lawrence Gilbert and Peter Raven; ‘Gulf Fritillary Butterfly, Agraulis vanillae (Linnaeus) (Insecta: Lepidoptera: Nymphalidae)’ by Jaret C. Daniels; ‘Novel chemistry of abdominal defensive glands of nymphalid butterfly Agraulis vanillae’by Gary N. Ross,Henry M. Fales, Helen A. Lloyd, Tappey Jones, Edward A. Sokoloski, Kimberly Marshall-Batty, and Murray S. Blum; and ‘Introduction to General and Applied Entomology, Third Edition’ by V.B. Awasthi. We thank the amazing arborists of Trees South Carolina and the Norfolk Botanical Garden for providing the inspiration for this Bug of the Week.

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Color and pattern of the gorgeous pipevine swallowtail warn predators of a nasty meal should they dare to attack. Image credit: Dr. Paula M. Shrewsbury

In recent years Bug of the Week has visited several beautiful butterflies whose dominant wing coloration is based on the theme of a black background with series of patches and spots in shades of white, orange, and blue. Butterflies participating in this cabal include the dark female form of the eastern tiger swallowtail, the pretty red-spotted purple, the eastern black swallowtail –eater of parsley and dill – and the clever spice bush swallowtail, whose larvae mimic serpents. Why have all of these beauties converged on a relatively common color scheme? 

Dutchman’s pipe is a favored host for Polydamas caterpillars. Eggs deposited on a growing tip will later hatch into very hungry caterpillars.

Caterpillars of the butterflies that we meet today, the pipevine swallowtail and the Polydamas swallowtail, dine on plants in the birthwort family, Aristolochiaceae, that include vines commonly known as pipevines. Members of this family produce a class of compounds known as aristolochic acids which are known to be mutagenic, carcinogenic, and toxic to kidneys of mammals. As they consume leaves of pipevine, these swallowtail caterpillars store these toxins and in turn pass them along to the adult butterflies and also to their eggs. Aristolochic acids sequestered by caterpillars may help protect them from attack by parasitic wasps. Adult butterflies are rendered distasteful to vertebrate predators such as birds by virtue of these noxious compounds. It is believed that birds attempting to eat butterflies whose larvae consumed pipevines have a nasty experience that teaches them not to mess with darkly colored butterflies. Other species of butterflies capitalized on the lesson taught by the pipevine and Polydamas butterflies by evolving color patterns to mimic their appearance, thereby gaining protection from visually astute predators. This type of mimicry, in which warning colors of a distasteful species like these swallowtails act as a model copied by other palatable butterflies, is called Batesian mimicry. The great English naturalist Henry Bates first described this form of mimicry while studying butterflies in Brazilian rainforests.

This gorgeous resting pipevine swallowtail will soon seek pipevines on which to deposit brightly colored orange eggs that hatch into tiny caterpillars. As the caterpillars feed and grow, they accumulate noxious compounds and take on a startling visage, complete with fleshy dangling appendages and orange bumps advertising their distastefulness.  Video credit: Dr. P. M. Shrewsbury

We met other species of Batesian mimics, such as harmless flower flies that mimic stinging bees and stilt-legged flies that mimic wasps. And adult butterflies are not the only creatures that mimic pipevine swallowtails. Recall that the caterpillars of these swallowtails are also laced with aristolochic acids. Scientists believe that a cyanide producing millipede with deep red coloration mimics the color and pattern of the pipevine caterpillar, thereby gaining protection from predators. We have also seen this mimicry before with several orange and black insects that eat milkweed, including monarch caterpillars, milkweed bugs, and milkweed tussock moth caterpillars.  This convergence on a similar, easily recognizable color pattern by two or more nasty-tasting insects is called Müllerian mimicry, named for the famous German naturalist Fritz Müller.

As this spectacular butterfly season comes to an end, try to grab one last glimpse of one of these dark winged beauties and ponder the question – model or mimic?

Acknowledgements

Bug of the Week thanks observant Dr. Shrewsbury for spotting adults and larvae of the pipevine swallowtail and providing the image and a video featured in this episode. “Secret weapons” by Thomas Eisner, Maria Eisner, and Melody Siegler, and the Featured Creature articles “Common name: pipevine swallowtail, blue swallowtail scientific name: Battus philenor (Linnaeus 1771) (Insecta: Lepidoptera: Papilionidae: Papilioninae: Troidini)” and “Common name: Polydamas swallowtail, gold rim swallowtail, tailless swallowtail scientific name: Battus polydamas lucayus (Rothschild & Jordan) (Insecta: Lepidoptera: Papilionidae: Papilioninae: Troidini)” by Donald Hall provided valuable insights into the clever ways of this week’s stars.

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A gorgeous Carolina mantid waits for a meal – or perhaps a mate who might be a dinner “guest”.

What a year this has been for insects in general, with banner populations of butterflies, moths, stink bugs, and many others. Not surprisingly, when populations of plant-eaters flourish, we often see an upswing in consumers higher up in the food chain. In previous episodes, we met the two amazing and beautiful foreigners that sit atop the invertebrate food webs in our landscapes, the European mantis, Mantis religiosa, and the Chinese mantid, Tenodera sinensis. This week we visit one of our native mantids, the Carolina mantid, that is turning up in record numbers in our area.  

The Carolina mantid ranges from the Canadian border into Mexico and from the east coast to Nevada and Arizona. Like other mantid species, Carolina mantids eat a wide variety of insects and spiders found in gardens and landscapes. And yes, on occasion the female consumes her unfortunate mate, especially so when mantids are raised in captivity. The extent to which this is an artifact of being raised under unnatural conditions is not known, but it is reported that well-fed gals are less likely to consume their suitors than hungry ones. Several of the mantids I have seen over the past week are gravid females, those carrying a full load of eggs. When enough prey has filled her belly and a lucky, or perhaps unlucky, male has contributed his sperm, the female will deposit her eggs in an egg case. The entomological term for the egg case is ootheca. A mantid’s ootheca is composed of frothy material called spumaline that has the look and feel of an elongated glob of Styrofoam. The female mantid secretes spumaline from glands in her abdomen as she deposits eggs, usually on vegetation or on structures such as fences and houses. The ootheca serves as a protective matrix for scores of tiny eggs resting within.

From afar, a very pregnant female Carolina mantid seems to have her sights set for incoming prey. As the camera invades her personal space, she gives the paparazzi the kind of “what are you looking at” stare that only a mantid can deliver. This disdain for bug geeks apparently starts early. Even juvenile Carolina mantids would rather groom their raptorial forelegs than indulge a guy with a camera. However, the arrival of a large carpenter bee can trigger a hasty retreat.

After emerging from the ootheca, tiny hatchlings take their first glimpse of a world full of wonderful morsels to eat and fearsome predators to be eaten by.

After surviving the chill of winter, eggs complete their development with the return of warm weather. Warm weather signals the return of foliage to plants and the presence of legions of small tasty insects that serve as food for developing mantids. Sometimes mantids will deposit eggs on vegetation that could find its way into a home, such as on a Christmas tree or pine garland. In the warmth of a home, eggs within the ootheca may develop and hatch, and become an extra special holiday surprise. With the holiday season not far away, perhaps it is time to make a mental note to inspect boughs and trees before they enter a home. 

Although egg cases of praying mantids can be purchased commercially and placed in the garden, the effectiveness of mantids as biological control agents is ambiguous at best. Remember, they are generalist predators and may capture and eat beneficial insects as well as pests, not to mention each other. Nonetheless, mantids are fascinating to observe and study and I always have an ootheca in my landscape to restock my garden with these marvelous creatures when spring returns. 

Acknowledgements 

Bug of the Week thanks Kathleen, the crew at MPT, and the staff and students at the Howard Conservancy for providing the inspiration for this episode.

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