Month: December 2019

 

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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