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A red admiral appears to survey the surrounding landscape from a small branch. Is it seeking a mate or getting ready to search for food?

In a previous episode, we met an electrolyte-seeking red admiral butterfly as it lapped salty perspiration from the back of a hand.  While meeting this butterfly up close and personal was fun, one of the pursuits of typical bug geeks is to observe not only adult insects but also their fascinating and sometimes-cryptic immature stages. The best hope to observe red admiral caterpillars rests on a visit to the moist forest where stinging nettle abounds.  You see, stinging nettles and other members of nettle family, Urticaceae, are favored hosts of red admiral caterpillars.  Having experienced great luck in spotting several red admirals, other brush-footed butterflies, and swallowtails in Shenandoah National Park, a return to nettle covered slopes of the verdant woodland forests seemed like the right move to hunt caterpillars.

After several failed attempts to find a shelter occupied by a red admiral, we hit pay dirt and found a few beautiful caterpillars inside their leafy redoubts. Video credit: M. J. Raupp and P. M. Shrewsbury

This mature red admiral caterpillar will soon form a chrysalis.

On the lower slopes of Hawksbill Mountain stinging nettles abound and red admiral butterflies are easily spotted along the rocky trail. Some caterpillars of butterflies, like those of black swallowtails, are easy to find as they feed in the open on their host plants. However others, like caterpillars of the silver spotted skipper and spicebush swallowtail, have a clever trick to avoid the ever-searching eyes of hungry predators. As they feed, young caterpillars fold and roll individual leaves of their host plant around their bodies, creating an edible shelter. As caterpillars develop and grow, several leaves may be bound together to form a very private and protective “nest.” Pupation also occurs within these leafy shelters.

Whether its extracting salt from a pebbly beach along the Potomac, lapping perspiration from the back of a hand, seeking nutrients from a weep-hole in a tree, or tasting the surface of a lawn chair, red admirals are fascinating to observe.  Video credit: M. J. Raupp and P. M. Shrewsbury

In the waning days of autumn, adults that emerge from pupae will begin a southward journey to warmer realms in Texas and further south to escape the rigors of winter temperatures. When winter releases its grip over much of North America, hibernating adults begin stirring and will soon undertake their journey northward to take advantage of fresh patches of nettles blanketing the forest floor. Two broods of red admirals occur annually throughout much of the United States. Red admirals are not unique to the United States and are found in parts of Central America, Mexico, Canada, several Caribbean Islands, New Zealand, Europe, Northern Africa, and Asia. Last week red admirals were very plentiful in butterfly gardens throughout the DMV, but you better hurry to get a glimpse of these beauties. With the first frost, a speedy exodus of our migrant butterflies to southern latitudes might be just around the corner.

Acknowledgements

Bug of the Week thanks Dr. Shrewsbury for wrangling and videoing red admiral caterpillars. Two superb websites, Butterflies and Moths of North America and Maryland Biodiversity Project, were used to prepare this episode, as was David Wagner’s remarkable Caterpillars of Eastern North America.

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A tiny silvery checkerspot caterpillar glides across the leaf’s surface on delicate strands of silk.

One of the real pleasures of spring is to buy a packet of sunflower seeds, plant them in the soil, and see what develops over the course of the growing season. Having selected a packet marked dwarf sunflowers, we germinated the seeds, grew potted seedlings, and installed them in a front flower bed with expectations of pretty sunflowers just tall enough for close observation at eye-level for children and adults. Little did we know that by the end of August, these sunflowers would exceed ten feet in height, dwarves only for exceedingly large humans or small giants. Fortunately, sunflowers and other members of the aster clan turn out to be excellent hosts for the wonderful silvery checkerspot butterfly, close cousin to the Baltimore checkerspot, state insect of Maryland.

A phalanx of stout spines helps protect the checkerspot caterpillar from the jaws of hungry predators.

The first clues of the checkerspot visit were severely skeletonized leaves. It turns out that the silvery checkerspot female deposits her eggs in large clusters. Upon hatching, tiny caterpillars feed in a great herd on the underside of a leaf, removing the tender tissue and leaving behind only a skeleton of veins and the papery thin epidermal layer of the leaf’s upper surface. By September, several leaves of the sunflower wore the signature of roving bands of caterpillars. Here in Maryland, two broods of silvery checkerspots occur each year, the second of which spends the winter as caterpillars in a protected location on the ground. These caterpillars complete their development the following spring with the return of warm temperatures and the appearance of tender leaves of Jerusalem artichokes, black-eyed Susans and other members of the aster family. Don’t be surprised to see pretty silvery checkerspots nectaring or basking on a wide variety of plants as summer turns to autumn. They can be seen from June through September and have been reported in every county west of the Chesapeake Bay here in Maryland.

Advertised as dwarf sunflowers, these giants soon wore the marks of roving bands of caterpillars as they grazed on leaves and danced in the sunlight. Fully grown caterpillars removed great chunks of foliage before pupating and turning into spectacular butterflies, nectaring and basking in the late summer sun.

Acknowledgements

Bug of the Week thanks Eloise and Abigail for providing inspiration and sharing their caterpillars. Caterpillar guru Karin Burghardt identified the hungry herd and the wonderful Maryland Biodiversity Project website and David Wagner’s “Caterpillars of Eastern North America” were consulted in preparation of this episode.

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A small black spot often with a white center on the inside of each front leg provides a quick clue to separate the European mantis from other species found in our region.

Late summer and early autumn are times when sightings of praying mantises often generate interest from gardeners here in the DMV. It’s not that mantises have spontaneously generated during this season. Rather, these cryptic sit-and-wait predators are pretty tough to spot earlier in the season when they are small and blending in with the foliage of plants on which they hunt. This week an eagle-eyed graduate student spotted a beautiful European mantis hiding in my flower bed.

This European mantis finds brown marmorated stink bugs delicious. Mantises are part of Mother Nature’s hit squad turning back the tide of invasive pests.

The European mantis was first discovered in the US in 1899 in New York State. It arrived apparently as a stowaway on a shipment of nursery stock from Europe. The name ‘mantis’ comes from the ancient Greeks who used the word mantis to describe a soothsayer, or one that could see into the future, and the future of this mantis in the New World has been bright. Since its introduction to North America, this magnificent creature has spread throughout much of the United States. It is now widespread east of the Mississippi and northward into Canada. In years past, European mantises have been invited into our laboratory to enjoy a life devoid of the predators so plentiful outdoors. In captivity our young mantises spend time cavorting in a terrarium and practicing their hunting skills on fruit flies, the mainstay of their diet. As they mature, these predators progress to larger prey such as grasshoppers, caterpillars, and crickets.

This brown egg case, or ootheca, contains scores of eggs that will survive the winter and hatch next spring.

As we learned in a previous episode of Bug of the Week, mantises have a disconcerting habit of eating each other. To prevent unfortunate dining experiences, our mantises are raised in isolation. As summer becomes autumn, our mantises turn their attention towards finding a mate. One particularly lovely femme fatale named Manti enjoyed dinner and a date with a charming, but hapless, and soon headless, gentleman named Little Richard. Manti later presented us with a spectacular egg case called an ootheca. The ootheca is a Styrofoam-like structure deposited by the female mantis on a structure such as a branch or trunk of a tree. A single ootheca may house more than one hundred eggs. Outdoors these eggs endure the inimical winter season safe inside the ootheca, and hatch when warm temperatures and abundant tasty prey return in the spring.

Mantises are not without their own predators. By day, birds hunt these marvelous insects. By night, as mantises fly about seeking food or mates, they are hunted by hungry bats. Bats use ultrasonic signals to detect prey such as moths and mantises in the dark. One might think mantises are helpless in defending themselves from these stealthy nocturnal predators. But mantises have a clever trick up their sleeve or, more correctly stated, a clever ear on their chest. Many species of mantises have evolved an organ to detect sound, an ear so to speak, on the underside of their thorax. Mantises use this ear to detect ultrasonic “chirps” emitted by hunting bats. When the soaring mantis detects the signals of a hungry bat, it evades the bat by quickly diving to the ground.

This morning I happened to spy my resident mantis resting on a milkweed plant enjoying a breakfast of a large milkweed bug. Milkweed bugs bear the orange and black color pattern of other milkweed feeders, including the monarch butterfly, that warn predators of noxious chemicals stored in their bodily tissues. In fact, studies of the Chinese mantid we met in a previous episode demonstrate its ability to learn not to consume nocent milkweed bug prey.  Maybe my European mantis has a more ironclad constitution than its eastern cousin. Or maybe this gastronomic adventure will turn into a dietary mistake. Tomorrow I will check and see if the mantis experienced any digestive distress. As you work in the garden over the next several weeks, keep your eyes open. It’s a good time to catch a glimpse of these beguiling ambush predators.

Hey milkweed bugs, guess who is coming to breakfast. That’s right, a European mantis. And guess what, you’re breakfast! 

Acknowledgements

Bug of the Week thanks Lizzie Dabek for spotting the mantis and providing the inspiration for this episode. The fascinating articles “Recent range expansion of the Praying Mantis, Mantis religiosa Linnaeus (Mantodea: Mantidae),in British Columbia” by Robert Cannings, “The midline metathoracic ear of the praying mantis, Mantis religiosa” by  David D. Yager and Ronald R. Hoy, and “Mantids and milkweed bugs – efficacy of aposematic coloration against invertebrate predators” by May Berenbaum and E. Miliczky, provided keen insights used in this story.

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An explosive season for fall webworms finds trees throughout our region festooned with silken webs.

We’ve had a lot of fun this season enjoying Lepidoptera, members of the moth and butterfly clan, where swallowtails, brush footed butterflies, and silk moths large and small have been featured. In this year of caterpillar glory, several of the not-so-nice moths, including Fall Webworm, have enjoyed a renaissance as well. Actually, the crescendo of Fall Webworm has been building over the past several years and this Bug Guy is hoping they have reached the climax in our region. Fall webworms are causing quite a mess. Complaints about their numbers have been coming in from Baltimore to Washington as they denude trees of leaves and festoon them with their messy, persistent webs.

Eastern tent caterpillars are spring feeders whose tents wind-up in the crotches of branches on preferred hosts like cherry.

 As I visited with folks this summer, several asked about these ubiquitous “tent caterpillars”. Let’s set the record straight: tent caterpillars, webworms, what’s the difference and how do you tell them apart? It’s easy. Eastern Tent Caterpillars (ETC) appear in March and early April in our area and build tents around branches in the crotches where branches diverge, or where limbs join the trunk. The common hosts of ETC are trees in the rose family such as cherry and apple. ETC leave the safety of their nests to feed on foliage along the branches, returning to their nests by evening after eating their fill. They will abandon their nests to pupate on the ground and emerge as adult moths in June and July. By contrast, Fall Webworms first appear in May and June and build expansive nests on the terminals (ends) of branches, incorporating the foliage they will feed upon. A second generation follows the first and in this year of moth and butterfly nirvana, they and their nests are super abundant through July, August, and September.

Inside the webs, fall webworm caterpillars devour leaves and deposit tiny mounds of frass.

Fall Webworms are one of the most catholic of all caterpillars and eat several common trees in our area including cherry, crabapple, maple, sweet gum, sycamore, and walnut. Fall Webworms are known to feed on more than 200 species of plants. Two distinct tribes of Fall Webworms have been described, one with black heads and others with red heads. In the latter half of August, we near the finale of webworm activity for the year. The webworm caterpillars in the nests will soon vacate their shelters to form pupae in the leaf litter and duff beneath trees, where they will spend the autumn, winter, and early spring. Next spring and early summer, adult Fall Webworm moths will emerge from the soil, find mates, and lay hundreds of eggs on the undersides of leaves. Tiny caterpillars hatch and spin small webs, first around their natal leaf and later around small clusters of leaves on the same branch. Inside the relative safety of these webs, larvae munch on leaves. As they grow, larvae enlarge the web to include ever-greater expanses of leaves and branches. When Fall Webworms are abundant, entire trees may be enclosed in these webs. After the first generation of webworms has developed, they move to the ground to pupate, produce new adults, and the cycle repeats. In Maryland, two generations of Fall Webworm are common annually, while in southern states such as Georgia and Texas as many as four generations occur each year.

 In most years and most locations, Fall Webworms do not cause serious damage to trees. However, their nests create a bad case of “ugly” that persists well into the winter. Of course, one easy way to be done with these messy guys is to simply remove them by hand or with pruners when you first see the nests. If nests are far above the ground, a pole pruner may be handy. And don’t just toss the nests aside or you may learn that the caterpillars can march right back up the tree. Place the nest in a bag and discard it. Fortunately for us, Fall Webworm cycles wax and wane in a given area with years of hordes followed by years of few.

A look inside a webworm nest often reveals caterpillars twitching nervously, and why not? A Polistes wasp has landed on the web, extracted a webworm, and turned it into a ball of protein ready for transport back to the nest, food for developing wasp larvae.

Larvae of parasitic wasps emerge from the body of a fall webworm after devouring its internal organs.

More than 50 species of parasitoids and 30 species of predators are known to attack and kill Fall Webworm in North America. People often ask if this is yet another invasive species from another land causing trouble in the US. Nope, this pest is a home grown native that loves our native trees. One issue that really makes me peevish is the ever-increasing influx of exotic and invasive pests we find in our landscapes and gardens. Just think about the misery caused by Japanese beetles, gypsy moths, and emerald ash borer. I am often asked if this is a one-way street, with the USA the recipient of nasty bugs and the rest of the world getting off scot-free. Absolutely not! One of our pesky “gifts” to the rest of the world is Fall Webworm. In the 1940’s this insect was accidentally introduced to Hungary from North America. It has now spread throughout large parts of Europe and Asia. In China, Fall Webworm is known as the North American White Moth and it has become one of the most devastating of all forest pests by damaging thousands of acres of trees each year. Alas, in a world with a global economy we seem destined to share a global biota.  

And that’s not all; deadly assassin bugs like this female wheel bug find fall webworms delectable even while giving a ride to a complacent mate. Yellow jackets also plunder fall webworm tents to bring juicy caterpillars home to feed their young.

Acknowledgements

 Bug of the Week thanks Dr. Shrewsbury for spotting the paper wasp extracting webworms from their nests. ‘Insects that Feed on Trees and Shrubs’ by Warren Johnson and Howard Lyon was used as a reference for this episode.

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Orange racing stripes and a pair of fleshy horns behind the head make the oakworm one cool looking caterpillar.

Orangestriped oakworms grow up to be handsome moths.

The spring and summer of 2019 have witnessed a renaissance of charismatic moths and butterflies. This season we visited beautiful brush-footed butterflies, spectacular swallowtails, and a bevy of stupendous silk moths including cecropia, promethea, and luna. Most of these wonderful moths and butterflies never become common enough to be considered pests and tend to consume plants that are not economically important. Of course, exceptions do exist. One gourmand shared her sad story of the disappearing dill, consumed by a hungry horde of black swallowtail caterpillars. This week we meet a duo of wild native silk moths that have a predilection for two of our most common and important landscape trees – oaks and maples. Periodically, oakworms and mapleworms cause a bit of trouble when Mother Nature presents conditions that favor survival of these caterpillars. Outbreaks can occur and caterpillar depredations are not uncommon throughout the range of these insects. Fortunately outbreaks are usually short lived and brought to closure by naturally occurring parasites and predators – Mother Nature’s hit squad.

In some years oakworms will strip oaks of leaves.

In Maryland, adult orangestriped oakworms first appear in May from pupae that survived winter and spring in the soil. These moths mate and females lay eggs on the underside of leaves of favored hosts including oak, hickory, and birch. Eggs hatch and the tiny larvae feed gregariously, first as skeletonizers removing small bites of leaf epidermis, but later by devouring leaves right down to the mid-vein. After completing development, caterpillars move to the soil to pupate and a second generation of adults issues forth to repeat the cycle. 

Telltale pellets of frass (insect poop, a technical term) beneath a tree can mark the presence of caterpillars feeding above.

The life cycle of the greenstriped mapleworm is similar to its cousin the orangestriped oakworm with respect to overwintering in the soil and emerging as adults in spring to colonize trees, where its eggs are deposited on leaves. Throughout much of its range there are two generations, but in the deep south there may be three or more. A critical part of the life cycles of both of these beauties is to drop from the tree when larval development is complete, burrow into soil to pupate, chill-out through autumn and winter, and emerge as an adult in spring ready to find a mate and lay eggs on leaves. Normally, the exodus-from-trees part of the game is relatively straightforward and merely involves dodging ground-dwelling predators like spiders and predatory beetles, and excavating a cozy chamber in which to pupate. However, humans have created a new challenge for earth-bound caterpillars in the form of paved walking and cycling trails. Last week while enjoying one such trail circling a small lake in Columbia, Maryland, I was astonished by vast numbers of oakworms and mapleworms running for their lives to escape the athletic shoes and bicycle tires of fitness-bound humans. Now, don’t get me wrong, these trails are treasures bringing adults and children into contact with the natural world, but oy vey, trails, sidewalks, and roadways are virtual no-bug lands for many six-legged creatures whose lives depend on soil!

Stripped leaves tell us oakworms are nearby and sure enough the cluster has moved several meters away to hide from enemies. After leaving the relative safety of the tree, the pathway beneath becomes a graveyard for unlucky oakworms. Further along the trail, a mapleworm searches for its next leafy meal. But on the ground, death is only a footstep away. Run for your lives caterpillars!

While enjoying my walk and dodging as many caterpillars as possible, I wondered how some of the carnage could be reduced. Perhaps parts of the trail could be closed during these caterpillar migrations or maybe small signs warning of caterpillar crossings could be installed beneath oaks and maples along the pathways. We do this for deer and other wildlife, right? Unlikely. However, toward the end of my walk a trio of mothers with children in tow stopped to admire an oakworm scurrying across the path. One remarked about the plight of the caterpillar, bent down, plucked the larva from the trail, and moved it to the safety of leaf litter along the trail’s edge. The children smiled. Maternal instinct and caterpillars creating a teachable moment for the next generation of naturalists. You go moms!            

Acknowledgements

Three great articles, “An integrated pest management success story: orangestriped oakworm control in Norfolk, Virginia, U.S.” by P. B. Schultz and D.B. Sivyer, “Orangestriped Oakworm” by Steve Frank and Stephen Bambara, and “Greenstriped mapleworm, Dryocampa rubicunda (F.), Lepidoptera: Saturniidae” by Steve Frank and Adam Dale, were consulted in preparation of this episode.  BOTW thanks Dr. Shrewsbury for spotting and wrangling caterpillars for this story.

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Iridescent cobalt blue and gold colors may warn predators not to consider the elderberry borer as a meal.

This week we return to the Shenandoah National Park where we recently met busy swallowtail butterflies sipping nectar and brush-footed butterflies visiting scat and collecting salt from perspiring hikers. We also met the fascinating flower longhorn beetles as they foraged for pollen from blossoms of plants in gardens and forests. This week we meet another member of the flower longhorn clan, perhaps the most beautiful beetle of all. In a patch of herbaceous vegetation along a trail, a gorgeous elderberry borer settled in for a snack just in time to be captured by the cameras. The startling hues of this blue and yellow beetle serve as a warning to predators not mess with this attention-grabbing large insect.

Elderberry, the plant host for elderberry borer larvae, grows in marshy meadows.

Adult elderberry borers feed on leaves and pollen from the flower heads of elderberry, and female beetles lay their eggs near the base of the elderberry plant.  Upon hatching, the tiny larvae bore into roots where they feed and develop on nutritious plant tissues. However, elderberry is chemically defended by potent cyanogenic glycosides, toxic compounds that are believed to be passed along from larvae to adults. A taste of these noxious chemicals during an attack may teach a predator that large blue and yellow insects are not to be included on the menu.

After dining on a tender leaf, it’s up, up, and away for the gorgeous elderberry borer (end of video at 15% actual speed).

Net-winged beetles are members of a mimicry ring bearing contrasting patterns of light and dark colors.

This warning coloration, a.k.a. aposematic coloration, of contrasting colors of blue and yellow is also employed by other distasteful insects, including beetles and moths in a mimicry ring known as Müllerian mimicry, so named for the great German naturalist Fritz Müller.  One group of beetles in the mimicry ring are those known as net-winged beetles. These conspicuous yellow and bluish black beetles ooze a repellent mixture of acetylenic acid and lycidic acid from their joints when attacked by predators. These potent antifeedants have been shown to dissuade attacks by birds, spiders, and beetles. The distributions of several species of net-winged beetles overlap broadly with that of the elderberry borer. A summer hike in forest or meadow may reveal one of these intriguing colorful beetles, pretty to observe but not for consumption.       

Acknowledgements

Bug of the Week thanks Dr. Shrewsbury for spotting the gorgeous elderberry borer and capturing an image. Two intriguing articles, “The effect of the Argentine ant on the threatened valley elderberry longhorn beetle” by Gary R. Huxel, and “Defensive Chemistry of Lycid Beetles and of Mimetic Cerambycid Beetles that Feed on Them” by Thomas Eisner, Frank C. Schroeder, Noel Snyder, Jacqualine B. Grant, Daniel J. Aneshansley, David Utterback, Jerrold Meinwald, and Maria Eisner, were used in preparation for this episode.

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Note the dusting of yellow pollen on the back, legs, and mouthparts of this pretty longhorn beetle.

Over the past several weeks we met several spectacular butterflies visiting flowers to obtain carbohydrate-rich nectar, the rich source of energy that fuels flight. Well, insects cannot live by sugar alone. Like you and me, insects need sources of protein to develop, grow, and complete vital developmental processes, including the production of eggs in the case of females. Plants don’t disappoint in this regard. In fact, the earliest pollinators of plants were likely beetles. Unlike butterflies or bees whose mouthparts are adapted to sipping nectar from blossoms, beetles have chewing jaws designed for biting and munching food. Early on in the pollination game, beetles learned that pollen was a rich source of protein and for more than a hundred million years, beetles have been pollinating flowering plants. While visiting gardens and meadows this year, I have frequently stumbled across several species of longhorn beetles in the subfamily Lepturinae, beetles commonly known as flower longhorn beetles. One look at their antennae, which often exceed the length of their body, lets you know why they are called longhorns. The fact that they are regularly found foraging in flowers for pollen gives you the other part of their common name.

In this year of abundant pollinators, several species of flower longhorn beetles can be seen on blossoms in gardens, meadows, and forests.

While adults visit gorgeous blossoms in broad daylight and consume pollen as a primary food source, the immature stages, the larvae, live a boring life quite literally. You see, immature stages of these interesting pollen eaters are equipped with powerful jaws capable of cutting galleries in hardwoods, including oaks and maples. As they bore beneath the bark of dead and dying trees, potent enzymes in their gut digest refractory polymers including cellulose, which is a major component of wood. Studies have found that this remarkable ability is due in part to the microbiome found in the gut of longhorn beetle larvae. It seems that certain fungi found in decaying wood are ingested along with the wood consumed by the larvae. These fungi breakdown cellulose, thereby making the nutrients available to the developing beetle larvae.  What an interesting partnership.

Next time you visit a coneflower, take a moment to look for curious flower longhorn beetles and enjoy a six-legged wonder that delivers double duty providing ecosystem services as both a pollinator of flowering plants and a recycler of dead and dying trees.  

Acknowledgements

Bug of the Week thanks Dr. Shrewsbury for providing images of longhorn flower beetles and the inspiration for this episode. Two interesting articles, “Records of Cerambycidae (Coleoptera) in Massachusetts with Notes on Larval Hosts” by Josef Vlasak and Katerina Vlasakova, and “ The Role of Ingested Fungal Enzymes in Cellulose Digestion in the Larvae of Cerambycid Beetles” by Jerome J. Kukor, David P. Cowan, and Michael M. Martin, were used to prepare this episode.

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Red-spotted purple butterflies are often seen in light gaps in the forest. Are they simply basking in the sun or foraging for salt deposits in the soil?

From insects to humans the element sodium is needed for physiological processes ranging from the contraction of muscles and firing of nerves to maintaining the fluid balance of body tissues. For many species of butterflies one consequence of consuming a diet rich in nectar is a need to find supplemental sources of sodium to make up for the relative lack of sodium in the nectar of plants. While carbohydrates abound in nectar, it turns out that nectar is notoriously low in other essential nutrients, one of which is sodium. To solve this sodium shortage, butterflies have evolved clever strategies to acquire the sodium they need. One of these behaviors is known as puddling. Puddling involves placing their proboscis on a substrate and imbibing sodium rich fluid found on substrate’s moist surface. Typical puddling substrates include bird droppings, animal dung, and mud – salt of the earth.

A shoulder glistening with perspiration provides much needed salt to a fearless tawny emperor butterfly.

Last week we visited beautiful comma butterflies and their pretty, spiny caterpillars while on a hike in the Shenandoah National Park. During the same adventure, temperatures soared into the upper 90’s and hikers became drenched in perspiration. Human sweat contains relatively large amounts of salt. As the day progressed and sweat moistened our skin and clothing, several species of brush-footed butterflies including commas, red admirals, tawny emperors and red-spotted purples took full advantage of this salt resource as they landed on exposed skin and moistened clothing to enjoy the salty treat. The elongated proboscis of the butterfly provided a slight tickling sensation as it lapped and absorbed small beads of perspiration on the back of my hand. During these encounters, salt-seeking butterflies displayed a complete lack of apprehension while feeding on a human. The drive for salt appears to be strong and capable of overcoming the fear of proximity to a large, potentially dangerous animal. Butterfly experts have discovered that the puddling game is played mostly by male butterflies. It turns out that during copulation, in addition to transferring sperm, a male butterfly may donate a large dose of sodium to his mate, obviating the need for her to seek additional sources of sodium. What a guy!

Tiger swallowtails, painted ladies, red admirals, and commas obtain much needed sodium from salt containing substrates on the ground and from skin or clothing moistened by perspiration.

 With lots of summer remaining and temperatures sure to reach the 90’s, take a hike in the forest, work up a little sweat, and treat some butterflies to the salt of the humans.  

Acknowledgements

Bug of the Week thanks Drs. Szczepaniec and Shrewsbury for posing with salt-seeking butterflies and providing the inspiration for this week’s episode. The fact-filled article “Nutrient acquisition across a dietary shift: fruit feeding butterflies crave amino acids, nectivores seek salt” by Alison Ravenscraft and Carol L. Boggs was consulted in preparation for this story.

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Angled wings with the mottled pattern of a dead leaf on the underside help the comma butterfly escape the searching eyes of predators. Note the bright comma-shaped mark on the hindwing that gives the comma its name.

Stinging nettles and feces don’t make Dr. Oz’s list for the ultimate keto diet, but for caterpillars and adults of the comma butterfly, these foods are just fine. Let’s return to Shenandoah National Park where last week we met tiger butterflies. This week we arrive at the picnic ground at mile post 62.8 for a visit with the clever comma butterfly. Here at the east end of the picnic grounds a trail descends to the spectacular South River Falls, the third highest waterfall in the park. As the trail snakes deeper into the gorge, the understory of a maturing deciduous forest is covered by stinging nettles. These members of the Urticaceae, with their stinging spines and tender leaves, wear the telltale signs of leaf-munching insects: sections missing from the margins, small and large holes riddling leaf blades. On one nettle we spotted the beautiful comma caterpillar basking in the dim light of the forest. Festooned with stout spines, a potent defense against the tender mouths of vertebrate predators, the caterpillar seemed content to rest in plain sight. Nearby, another late instar larva strolled across lichen colored stones, perhaps on its way to find a tender-leaved nettle for dinner. Early stages of the comma are not so bold and hide beneath leaves when not feeding.  

Is this gorgeous comma caterpillar dashing off to find more food?

A little further down the trail we met hikers accompanied by their friendly canine companions. Fortunately, these pooches left deposits of former meals in small and large piles along the trail. Nutrient rich vertebrate scats are used by a variety of insects, including other brush-footed butterflies and broad-headed bugs we met in previous episodes.  Dung is a food source particularly rich in nitrogen, an element necessary for the growth and development of all living organisms, including insects. Commas have added scat to their menu, which also includes rotting fruit and carbohydrate-rich tree sap.

Watch as a pair of comma butterflies battle to see who can be ruler of the dung.

Stout spines help defend the comma caterpillar from attacks from hungry predators.

While comma caterpillars are protected by nasty spines, adult commas use another form of defense – crypsis. Unlike other butterflies and moths whose wings have smooth rounded margins, comma butterflies and their kin have forewings and hindwings bearing deep notches that break-up the typical butterfly outline. This gives rise to the common name for these butterflies that are known as angle wings. In addition to the uncharacteristic body outline, the underside of the comma’s wings strongly resembles a dead leaf. This masquerade helps the resting comma avoid detection by the searching eyes of hungry predators. Fortunately, throughout its range in the DMV the comma has two generations each year so there is still plenty of time to go for a hike, find some scat, and enjoy the antics of the marvelous comma butterfly.

Acknowledgements

Bug of the Week thanks Dr. Shrewsbury for spotting the peripatetic comma larva that inspired this episode and Dr. Burghardt for confirming the identification of the larva. The marvelous web site Butterflies and Moths of North America was used as a reference for this episode.

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