Ancient insect in a modern world: Silverfish, Lepismatidae

This week let’s time travel a little bit. Not the teeny, across the centuries travels Claire Fraser undertakes in Outlander. Nah, let’s journey back hundreds of millions of years long before T. rex walked the earth to the ancient origins of insects. In times when giant tree ferns ruled earth’s forests, primordial relatives of silverfish, the Triassomachilidae, foraged for starchy remains of plants on the verdant forest floor. Now fast forward several hundred million years to last Tuesday, when a handsome silverfish appeared at 6:10 am on the bathroom wall. With ancient decaying tree ferns conspicuously absent from my home, I wondered what delicacies silverfish discover inside a residential dwelling.

Among the most ancient of insects are the silverfish. On rare occasions I am graced by their presence early in the morning on my bathroom wall or maybe in the sink. My catch and release policy ensures they can find more natural surroundings when I release them outdoors.

Actually, we share many carbohydrate-rich food sources with plants found at the time of the world’s first silverfish. Modern food on the silverfishes’ menu include those high in starchy materials such as the cellulose found in paper goods and glue, the kind you were told not to eat in first grade, the glue that binds pages of books together. It is not surprising then, that some species of silverfish are important pests in libraries and museums where starchy materials abound. Other tasty treats for silverfish include natural fabrics such as linen, silk, and cotton, cereals, preserved meat, and dead insects, including other silverfish. Of course, in the geological time scale, frame houses are a fairly recent contrivance and typical natural habitats for silverfish are decaying logs and leaf litter, caves and crevices, and, for some species, ant nests.

The name silverfish was coined in part from the silvery scales found on the insect’s exoskeleton. The “fish” part apparently refers to the resemblance of the silverfish’s scales to those of fish. If you find silverfish scurrying around your home and wonder about the source, have a close look in dark, damp corners of the basement or other places where books or garments might be stored. Infested books or clothing can be placed in plastic bags and deposited in a freezer for a few days to kill attendant silverfish. Silverfish also thrive in conditions of high humidity and dehumidifiers placed in damp rooms may help reduce the suitability of these locations for silverfish. Removing clutter, storing books and garments in airtight containers, and vacuuming closets and storage areas will also help reduce populations of silverfish and other nuisance pests around the home. So, where is the wellspring for my silverfish? Well, just beneath my bathroom floor lies a pantry used to store paper goods and other household items. Sometimes it is a bit musty and maybe it could use a more regular visit with a vacuum. But, I have to admit, there is something remarkable about a morning greeting by a creature older than dinosaurs. I usually just catch these old timers in a paper cup, warn them to socially distance especially when predators are near, and release them in the wild.  

Acknowledgements

To learn more about silverfish, please check out the fascinating fact sheet “Common name: silverfish, scientific name: Lepisma saccharina Linnaeus (Insecta: Zygentoma: Lepismatidae), Introduction – Distribution – Description – Life Stages and Biology – Hosts – Economic Importance – Survey and Detection – Management – Selected References” by Eleanor F. Phillips and Jennifer L. Gillett-Kaufman. It can be found at this link: http://entnemdept.ufl.edu/creatures/URBAN/silverfish.HTM

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Next weekend we celebrate Valentine’s Day, a day named in honor of a third century Italian saint commemorated throughout the centuries by exchanging notes of love, romance, gifts of flowers and candy, and boatloads of affection. Several amorous characters take center stage in this Bug of the Week. Whether it’s a horny male Hercules beetle out for a romp on a stump, wheel bugs enjoying an intimate dinner of fall webworm caterpillars, or teenage cicadas celebrating a day in the sun after seventeen years underground, conjugal visits abound in the insect world. Let’s find out why.

For many animals, copulation is a short-term affair, measured in mere minutes or sometimes fractions thereof. However, insects depicted in this episode linger long with their mates, in some cases copulation lasts for hours and even days. Red-shouldered bugs we met in a previous episode may copulate for eleven days. How exhausting! Prolonged copulation and post-copulation “riding” of a male on the back of its mate is common in many orders of insects. By denying interlopers access to a female, prolonged mating and post-copulatory guarding by the male helps ensure that his sperm will be the ones which fertilize his mate’s eggs. In the world of insects, often the last mating before eggs are laid is the one that counts. This likely explains the oft observed pairings of so many male and female insects.  

Long before Disney coined the term “Love Bug” for a rambunctious Volkswagen beetle, denizens of Florida and the Gulf states knew of another kind of lovebug. The Floridian lovebug is a small fly with a red thorax and black body and wings. The name “lovebug” derives from the fact that these small flies are often found intimately entangled. Lovebugs belong to a family called the Bibionidae. As larvae, bibionids eat decaying plant material and are important decomposers like isopods we met in a previous episode. After completing development in the soil, they pupate and emerge as adults. Adult flies do not bite or sting, but vast numbers emerge in spring and fall creating a real nuisance to residents in southern states. In addition to entering homes and bumbling about the garden, lovebugs splatter windshields of cars and trucks creating hazardous driving conditions. They become numerous enough to clog radiators of cars, causing them to overheat. One way to avoid these lovers is to drive in the late afternoon or evening when lovebugs are less likely to take wing.

Many Insects have prolonged copulation and often males guard their mates for hours or days following copulation. Just for fun, let’s look at a few. From first to last, they are: Damselflies coupled in the “heart” position for long periods of time; conjoined spur-throated grasshoppers basking in sun; camera-shy periodical cicadas that will appear by the trillions this spring when Brood X appears; peripatetic milkweed bugs playing push me, pull you; gorgeous dogbane beetles enjoying dinner and a date on their heart-stopping host; male margined carrion beetles engaging in shaky business with their mates; female thread-waisted wasps dining on pollen while their mate hitches a ride; and adorable male horn-faced mason bees fending-off suitors while guarding their betrothed.  

With respect to kissing and kissing bugs, many would agree that kissing ranks right at the top when it comes to affection. However, the kiss of the kissing bug can be oh, so much more than that. Kissing bugs belong to a family of sucking insects called assassin bugs. Assassin bugs are predators, predators with long beaks which they use to suck blood from many other kinds of animals. Kissing bugs take the act of predation one step further. Their primary source of food is the blood of vertebrates, including mice, dogs, and humans. During the day, kissing bugs hide in crevices in plaster, cracks between boards, or in gaps in thatched roofs. At night, these little vampires leave their refuge and quietly seek unsuspecting humans to suck their blood. They may feed on any exposed body part, but look out, their dining preferences swing to tender tissues on people’s faces, especially the lips, hence the name kissing bugs. In southern Texas, Central and South America, kissing bugs are common. For most people the bite of the kissing bug may go unnoticed, or it may leave no more than a small red mark. But for those allergic to the saliva of kissing bugs, itchy welts, rashes, and swelling can occur. As with the introduction of any foreign protein into the body, anaphylactic reactions are a concern. A greater worry associated with kissing bugs is their ability to vector a nasty parasite called Trypanosoma cruzi, the causal agent of a sometimes fatal disease called Chagas disease. The parasite is ingested by the kissing bug as it feeds on an infected animal. Carried in the gut of the kissing bug, the parasite issues forth when the kissing bug defecates on a victim’s skin. An abrasive scratch by the victim or a small puncture in the skin allows the parasite to enter the body and wreak havoc. How disturbing! While most common in regions of Central and South America, kissing bugs can be found as far north as Pennsylvania on the east coast and California on the west coast. If your adventures take you to rural areas of Mexico, Central or South America where Chagas disease is endemic, always sleep inside your netting and remember, no kissing the kissing bugs, even if it is Valentine’s Day!

Acknowledgements

The intriguing article “The adaptive significance of mate guarding in the soapberry bug, Jadera haematoloma (Hemiptera: Rhopalidae)” by Scott P. Carroll, the great Featured Creature fact sheet “common name: lovebug scientific name: Plecia nearctica Hardy (Insecta: Diptera: Bibionidae) Introduction – Classification – Distribution – Description – Key to the Species – Dilophus sayi – Behavior – Hosts – Economic Importance – Management – Selected References” by H.A. Denmark and F.W. Mead,  and the CDC Chagas disease website were consulted to prepare this episode. Bug of the Week thanks Marcia Shofner for the inspiring this heart-warming Valentine’s Day episode.

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This week we turn to the Bug of the Week mailbag where we received a picture of an unusual winter-active insect found on the trunk of a tree. Let’s visit stoneflies, curious amphibious insects whose lives are split between two worlds; a life aquatic in their youth and romantic interludes on land as adults.  While many insects migrate or enter a hibernal torpor called diapause during this frosty season, winter stoneflies are in their glory. Special compounds including glycerol, proteins, and sugars act like antifreeze and prevent stoneflies from freezing to death as they cavort on snow covered stream banks. These ancient insects can be found on stones, vegetation, and bridges near small, fast-moving streams. These week’s star was sighted in a nursery near a major river in western Maryland loitering on the bark of a tree. 

Adult winter stoneflies are dark brown or black and are active day and night. In their youth, stoneflies live in fresh water, rushing streams and rivers. Juvenile winter stoneflies, called nymphs, graze on submerged aquatic vegetation or decaying organic matter. Other species have abandoned a vegan diet and eat aquatic insects, including other stoneflies. Stonefly nymphs obtain oxygen from the water through delicate gills lining the neck, thorax, or abdomen. Most immature insects shed their skin or molt just a few times as they develop. However, some species of stoneflies may molt more than 20 times before leaving the water as adults in search of mates. The remarkable transformation from nymph to adult transpires at the edge of the stream as the nymph emerges from the water and latches onto a stone, log, or plant. The exoskeleton splits along the midline and the adult stonefly emerges like a wraith from the cast skin. When the exoskeleton hardens, adults walk and fly to find mates. As adults, food choice differs on a species basis. Some eat lichens, algae, or vegetation, but others gain all necessary nutrients as nymphs and never feed as adults. Winter stoneflies are relatively weak fliers and seem to prefer walking and running to flying. However, other species of stoneflies are good fliers and are attracted to porch lights and, unfortunately, bug zappers.

Stonefly courtship is a curious matter. A hopeful guy stonefly strikes the surface of a resting place, such as a small branch or a stone, with its abdomen to create a specific drum beat. If a female of the same species is nearby and favorably impressed by his rhythm and sound, she will drum a reply with her abdomen. The percussive duet continues and if both like what they sense, the deal is sealed and they mate. After mating, the female stonefly will swoop to the surface of the water to deposit her eggs. This is a season of joy for fish living in stonefly laden streams. Trout, steelhead, and other freshwater fish find stonefly nymphs and adults delectable. Both adult and juvenile stoneflies are an important source of food for denizens of our streams. Fisherman have taken advantage of this passion and created a variety of lures that mimic stoneflies with colorful names like Montana Stone Yellow and Henry’s Fork Yellow Sally.

Plucked from a riverbed, a stonefly nymph dashes to return to its watery realm. Shed skins of stoneflies cling to logs and stones near riverbanks where nymphs molt and become adults. On wintry days, males roam icy landscapes and even slowly moving humans in search of mates. Male stoneflies drum their abdomen on substrates including small branches and stones along the river to attract a mate. While inaudible to the human ear, a receptive female will catch his vibe and signal her willingness to mate by returning his percussive performance with one of her own. Who says drummers aren’t romantic?

Stoneflies are also important indicators of water quality. Streams with heavy sediments, low oxygen content, or pollutants do not support a diversity or abundance of stoneflies. Stoneflies emerging from your local stream are a positive sign of a healthy environment. So, during the next couple of weeks, take a walk on a sunny afternoon and visit a small stream or river to seek the stonefly. The best viewing is when stream banks are covered with snow and stoneflies clamber from the chilly waters below. The winter stoneflies featured in this Bug of the Week were observed on warmish afternoons on a small footbridge spanning the Little Patuxent River in Columbia, Maryland, on the Billy Goat Trail along the mighty Potomac River in Maryland, near the Monocacy River in Frederick County, Maryland, and along the banks of Pidcock Creek near Lambertville, Pennsylvania.

References

Bug of the Week thanks Steve Black for sharing his great image of a winter stonefly discovered on a tree-trunk. The fascinating book “Aquatic Entomology” by W. Patrick McCafferty was used as a reference for this Bug of the Week. Here is a link to a really nice article detailing the stonefly’s clever strategies for surviving winter: https://blogs.scientificamerican.com/guest-blog/winter-stoneflies-sure-are-supercool/

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By some unusual circumstance, Bug of the Week escapes the chilly confines of the Maryland winter and visits scenic Zion National Park and the Great Basin Desert, where we encounter entertaining and unorthodox darkling beetles called desert stink beetles. You’ll remember last week we met cousins of these gymnastic beetles called forked fungus beetles as they battled for possession of bracket fungi and potential mates. 

On the desert floor as day waned, these large and very juicy scrumptious looking darkling beetles appeared and wandered about feeding on vegetation with impunity. At close to an inch in length, these jet-black behemoths were highly conspicuous against the light red desert earth. With hungry predators such as lizards, birds, and rodents roaming about, the desert is a dangerous place for large, tasty-looking insects. As I crouched to photograph a beetle, it halted, stood on its head and lifted both pair of hind legs off the ground like some contortionist from Cirque du Soleil. What manner of trick was this? As I examined the creature a bit more closely with my fingers, my reward was a distinctly unpleasant odor emanating from the rear end of the bold beetle. Later my fingers turned a curious shade of brown where chemicals squirted by the beetle reacted with the air and my skin. 

Defenses of the desert stink beetle: First, when you see a human with a camera, run for grassy cover. Second, if he has you cornered and pokes at you with his giant finger, stand on your head and kick at him. Third, if all else fails, just lie on your back, legs in the air, play dead, and maybe the idiot will get bored and leave you alone. That worked.

This marvelous denizen of the desert was a darkling beetle in the genus Eleodes. Eleodes has evolved an elegant defense against other animals that would like to make it dinner. Dr. Thomas Eisner discovered that within the abdomen of Eleodes two large glands produce several types of quinones and other organic compounds. These noxious chemicals cause extreme irritation to mucus membranes such as those lining the mouth and eyes of predators like birds and toads. Quinones are also repellent to hard-core invertebrate predators like ants. Eisner suggested that the “headstand” routine may serve as a warning to would-be attackers to leave Eleodes alone or suffer the irritating consequences. It appears that at least one crafty desert predator, the grasshopper mouse, has devised a way to circumvent the beetle’s defense. Upon encountering its prey, the grasshopper mouse flips the beetle around and jams the beetle’s rear end into the soil. With the beetle’s chemical defenses shooting harmlessly into the dirt, the grasshopper mouse consumes the beetle, starting with the head, of course. When it comes to dining on Eleodes beetles, the grasshopper mouse has learned that one bad turn deserves another. 

Acknowledgements

We thank Mike, Brian, Anne, and Jim for the inspiration for this Bug of the Week, and  Dr. Shrewsbury for wrangling stinky beetles. The wonderful book “For Love of Insects” by Thomas Eisner served as a reference for this episode.

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Wood is composed of several compounds but, most notably, two really tough polymers you probably have heard of called cellulose and lignin. Fungi are one of but a few organisms able to breakdown these carbon-rich compounds and return these molecules to food webs. Without fungi recycling fallen trees, our forests would cease to exist as the dynamic wonderlands we enjoy today. Fungi turn wood into hyphae and fruiting bodies which in turn become food for creatures higher up the food web, including hundreds of species of insects. This week Bug of the Week dives into the email bag to share some marvelous images of really cool beetles whose lives depend on fungi as a source of food and as a stage for romance.

The forked fungus beetle belongs to a large family of beetles called darkling beetles, Tenebrionidae (previously we met other members of this clan in their winter refuge beneath the bark of a tree).  As their name implies, both larval and adult forked fungus beetles consume and thrive on nutrients contained in the tissues and spores of fungi. Bracket fungi in the genera Ganoderma and Fomes are reported to be favored hosts. Female beetles deposit eggs on the surface of the bracket fungus and larvae tunnel in and feed on nutritive hyphae. The forked fungus beetles we meet today were photographed in September 2020 on the surface of the bracket fungus where courtship battles often take place. The large horns curling above the head of the fungus beetles occur only on males. They play a key role in competitive interactions with other males for opportunities to mate with very cute but hornless female beetles.  Male beetles can often be found guarding bracket fungi where they chase away other males, potential rivals, and thereby monopolize the critical resource needed by females to lay eggs. One study found that males with larger horns had a greater chance of mating success than males with smaller horns.

Combat between two forked fungus beetle (Bolithoterus cornutus) males. The larger attacking male uses his clypeal horns in an attempt to dislodge the smaller male. The smaller male was previously courting the female and during the combat grips her with all six legs. The video has been sped up to 5x actual speed. Please visit the source of this video in the following amazing article: K.M. Benowitz, E.D. Brodie III, V.A. Formica (2012) Morphological Correlates of a Combat Performance Trait in the Forked Fungus Beetle, Bolitotherus cornutus. PLoS ONE 7(8): e42738. https://doi.org/10.1371/journal.pone.0042738

In addition to the prominent horns curling above the head of the male, a smaller pair of horns is present near the eyes at the front of the beetle’s face. So, other than looking marvelous, of what use are the horns? As part of the mating ritual, a male beetle will climb atop his mate and guard his intended for up to five hours while intermittently attempting to mate with her. Scientists have observed amorous male beetles using their two sets of horns “like a wedge and a bottle opener” to dislodge already engaged males from the female and thereby assert themselves as the winning suitor. In this battle to procreate, scientists have found that large beetles, ones with larger horns, are stronger than smaller beetles. Their powerful grip may make big beetles with big horns more difficult to dislodge from their mate than smaller males with puny horns.  In forked fungus beetles and many other animals, yes, size does matter.

Acknowledgements

We thank Cathy Keifer for providing the inspiration and marvelous images used in this episode. The remarkable articles “Morphological Correlates of a Combat Performance Trait in the Forked Fungus Beetle, Bolitotherus cornutus” by K.M. Benowitz, E.D. Brodie III, and V.A. Formica, and “Common name: forked fungus beetle (suggested common name) Scientific name: Bolitotherus cornutus (Panzer) 1794 (Insecta: Coleoptera: Tenebrionidae)” by Ummat Somjee and Andrea Lucky provided information used in this episode. Please learn more about forked fungus beetles at the following links:

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0042738

http://entnemdept.ufl.edu/creatures/misc/beetles/forked_fungus_beetle.htm

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On chilly days, most small invertebrate creatures like insects are locked in winter torpor awaiting spring’s warmth. However last week, following a nighttime low in the teens and with hoar frost still on the ground, I was delighted to see a gang of pillbugs, a.k.a. rollie pollies, sowbugs, potato bugs, or woodlice, slowly going about their task of recycling organic matter beneath a large bolt of a fallen ash tree. Unlike predators such as lady beetles or praying mantises that occupy exalted places high in the food webs, detritivores occupy lower rungs on the ladder of life. Detritivores are key players in Mother Nature’s clean-up crew. Their important task is to eat dead and decaying things such as fallen plants and return minerals locked-up in leaves, fruits, and woody tissues to the nutrient cycle. We visited other recyclers in previous episodes including rhinoceros beetles, millipedes, termites, and bess beetles.  

Early one morning, with frost still on the ground, a scrum of pillbugs huddles beneath a log. As the early morning sun warms their bodies, fourteen legs help them skitter from the sunlight to find danker refuge beneath the bark.

Isopods are not truly bugs, so please excuse their guest appearance in Bug of the Week, but they are odd and fascinating members of the arthropod clan. They belong to a group of hard-shelled creatures called the crustaceans. Crustaceans include tasty, familiar edibles like crabs, lobsters, and crayfish. Isopods commonly occur in marine environments where they eat algae, diatoms, and decaying vegetation. Eons ago, some adventurous members of the isopod lineage moved from the sea to the land. These explorers were the ancestors of the isopods commonly found beneath logs in the forest and those in my compost heap. Most gardeners know these curious creatures by the names pillbug or sowbug (a closely related terrestrial crustacean). The name pillbug stems from the ability of many species of these isopods to roll into a pill-shaped ball when threatened much like an armadillo. This defensive posture makes the tender underbelly of the pillbug difficult to reach. Armor-like plates on its back shield the pillbug from attack.  

With the return of warm weather, pillbugs will once again begin the important job of recycling my leftover vegetables. And in this taste test, it looks like carrots are preferred to tomatoes.

Pillbugs are common in moist habitats beneath leaf litter, compost, rotten logs, boards, and stones. Moisture is a key element in the life of isopods. Even though they have escaped the confines of a life aquatic with their colonization of land, these true crustaceans still rely on gills for the exchange of oxygen and carbon dioxide and those gills must remain wet. Unusually wet seasons like ones we have experienced in recent years create favorable conditions for explosions of pillbug populations. While pillbugs and sowbugs play an important role as recyclers, when too numerous they may damage the tender roots and stems of plants in greenhouses or gardens. Folks sometimes are dismayed when pillbugs appear in basements or garages as they move about in search of dead things. You can thwart entry of pillbugs into your home by using a few simple tricks: keep mulch away from foundations, maintain door sweeps, and caulk openings to discourage unwanted visitors from entering your home. With the return of warm weather in a few months, my compost heap will be a smorgasbord of rotting vegetables and, without fail, pillbugs will appear from the moldering depths of the bin eager to recycle plant remains. 

 Acknowledgements

We thank Dr. Shrewsbury for wrangling lumber, photographing pill bugs, and providing inspiration for this Bug of the Week.

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As we say good riddance to 2020, and welcome in a hopeful 2021, Bug of the Week will spend some time catching up with a few fascinating, fearsome, and funny creatures found in and around our homes. This week we visit tiny recyclers of organic matter called carpet beetles that can sometimes become pests. On a warmish winter day, I occasionally spot a rather lovely small beetle scaling a wall or scooting across a countertop in my home. Carpet beetles get their name from their proclivity to breed in a wide variety of natural substrates containing the protein keratin, which is found in felt, silk, feathers, pet hair, animal hides and carcasses, and, yes, woolen carpets. They become pests when colonizing a drawer, closet, or box where sweaters or other garments are stored. Adult beetles deposit eggs that hatch into hungry, tiny larvae which nibble away fibers, creating holes or sinuous trails in fabrics.

The larvae are very hairy little beasts, covered with long hairs or setae. Prolonged exposure to these hairs festooning the bodies of carpet beetle larvae has caused dermatitis in some people. Carpet beetles belong to a larger clan of recyclers called dermestids, or hide beetles. Hide beetles provide an important service to museum curators by virtue of their ability to strip skeletons of virtually all muscle and sinew, producing lovely bare bones. However, dermestids create problems for professional and amateur entomologists when they invade collections of pinned and preserved specimens. Larvae bore into dead insects and consume proteinaceous tissue within.  As they feed, small pellets of waste products called frass litter the area beneath the infested specimen. This is the classic hallmark of a dermestid attack. 

During winter, pretty carpet beetle adults and their very hairy larvae sometimes wander about my desk, table, and walls. In the wild, other dermestids are some of the last visitors to animal carcasses. Larvae like this one can remove skin, muscle, and other connective tissue, leaving behind nothing but bone.

Thwarting carpet beetle infestations is relatively straightforward. Before storing any garment made of natural fibers be sure it is laundered or dry cleaned and stored in a sealable bin or bag. If these rascals have already established a foothold somewhere in your home, try to ferret out their location. This could be a seldom used woolen rug in the basement, a box of sweaters in the attic, or a blanket, dress, or sport coat in a closet. Carpet beetles can also breed in carcasses of dead insects so maybe a pile of dead stink bugs in the attic is the source of an infestation. Some species of dermestids breed in stored products like grains, pet food, nuts, and spices. We met a caterpillar with similar habits, the Indian meal moth larva, in a recent episode. Once you locate the infestation, discard or destroy the material serving as the source of the infestation. In the case of carpets and rugs, vacuuming and deep cleaning will help. A lightly infested blanket or scarf can be salvaged by either placing the item in a deep freezer that is below 0 degrees Fahrenheit for several days, or by heating it above 130 degrees Fahrenheit for several hours. Temperature extremes can kill eggs, larvae, pupae, and adult carpet beetles. But please don’t set the item on fire or burn your house down.

How does a person who should know better wind up with carpet beetles in a home? The answer lies in the back of a closet where show-and-tell bugs used in STEM outreach are stored. In a tray of preserved scarab beetles, one unfortunate specimen bears an untidy deposit of frass attending its rear-end.  Since dead beetles don’t engage in post-mortem voiding of waste, the pile of frass is the tell-tale signature of carpet beetle larvae dining inside the dead scarab. Bad luck for the scarab translates to good luck for sharing a tale of carpet beetles.    

Bug of the Week wishes everyone a happy and healthy New Year free of all plagues!

Acknowledgements

 Information in this episode originated in great articles written by Whitney Cranshaw at Colorado State University and Michael Potter at the University of Kentucky. Learn more about these creatures at the following websites:

https://extension.colostate.edu/topic-areas/insects/carpet-beetles-5-549/

https://entomology.ca.uky.edu/ef601#:~:text=University%20of%20Kentucky%20College%20of,feathers%2C%20skins%2C%20and%20leather

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One of the real delights of the holiday season is adding festive plants to the home décor. As we have seen in previous episodes of Bug of the Week, this often means that some six and eight-legged creatures including mantises, adelgids, and spiders sometimes accompany a Christmas tree when it arrives indoors. These plant-related holiday surprises are not limited to Christmas trees, oh no. This week, let’s visit another fascinating but dastardly insect that sometimes makes its presence known on one of my favorite holiday plants, poinsettia. Decorating the home with poinsettias is a holiday tradition that likely originated in Mexico, where poinsettias add beauty to holiday nativity crèches. According to legend, in the town of Cuernavaca a young girl had no flowers to adorn the nativity at her church. Instead, she collected a weed growing by the roadside. An angel transformed the weed into the beautiful poinsettia, and ever since, poinsettias have been used as a seasonal decoration. Poinsettias are as much of a holiday tradition as mistletoe, holly, and an evergreen tree in many homes.  

As I browse displays of poinsettias that have sprung up in every hardware and grocery store, I’m on the lookout not just for holiday decorations, but for holiday whiteflies. Whiteflies are small sucking insects and relatives of more commonly known sap-suckers such as beech and woolly alder aphids we met in recent previous episodes. To spot a whitefly-infested poinsettia, first look at the color of the plant’s leaves – not the red, yellow, or speckled bracts comprising the blossom. The leaves on most varieties should be a clear deep green with no evidence of yellow patches or streaks. Leaves with yellow patches that are undersized, twisted, puckered, or curled can be the ghost of holiday problems yet to come. Whiteflies are usually found on the underside of leaves where they insert tiny beaks into the plant’s vascular system to extract sugar-rich sap from a vascular element called phloem. Plant sap contains nutrients needed for their growth and development. Large populations of whiteflies can cause leaves to drop prematurely. As whiteflies feed, they excrete a sugary waste product called honeydew. This sticky liquid can become a substrate for the growth of an ugly fungus known as sooty mold.  

Whiteflies have four stages in their lives, egg, nymph, pupa, and adult. An adult female whitefly lays eggs on the undersurface of a leaf. After several days, eggs hatch and mobile nymphs, called crawlers, move about the leaf surface until they find a suitable place to feed. Nymphs hunker down, shed their skin, and become stationary for the remainder of their youth. After several molts, a pupa forms, and from this pupa emerges the adult whitefly. Shed pupal skins often festoon the undersides of leaves. Adult whiteflies look like tiny white moths. They too have sucking mouthparts and suck the sap of poinsettias. If disturbed, they flutter from the leaf surface. The nymphs and pupae are usually yellowish or whitish and translucent. Red eyespots can be seen on the pupa shortly before the adult whitefly emerges.  

With wings yet to unfold, an adult whitefly emerges from its pupal case. A bit later with wings now fully expanded, polishing up the thorax and antennae is the next order of business to get ready for the holidays.

For the folks that grow poinsettias, whiteflies can be a very serious problem. If populations become too great, entire crops are lost. The most common whiteflies that come home with poinsettias are the greenhouse whitefly, Trialeurodes vaporariorum, and the silverleaf whitefly depicted in this Bug of the Week. A strain of silverleaf whitefly, the dastardly “Q biotype”, has been found in several states in the US. This strain is resistant to many of the pesticides formerly used to control whiteflies and causes headaches not only for the greenhouse industry but also for growers of some of our most important agricultural crops including tomato, peppers, squash, cucumber, beans, eggplant, watermelon, cabbage, potato, peanut, soybean, and cotton. Fortunately, entomologists are finding new ways to control whiteflies using tiny wasps that attack them, predatory beetles that eat them, and pathogens that give them lethal infections.  

If this Bug of the Week sounds a bit like the Nightmare before Christmas, try not to panic. Don’t let a few whiteflies on your poinsettia spoil the holiday. A few whiteflies will not ransack your poinsettia between now and the New Year and, hey, many poinsettias will join other decomposing vegetation in the compost well before Valentine’s Day. However, if whiteflies are numerous and your poinsettia looks whipped, and you had planned to keep your poinsettia going with the other house plants, it may be best to toss it out and replace it with one not bearing tiny six-legged gifts. Many fine, pest-free poinsettias can still be had in retail markets large and small. So, Happy Holidays to poinsettias, whiteflies and all!

 Acknowledgements

 The University of Florida Extension publication “Sweetpotato Whitefly B Biotype, Bemisia tabaci (Gennadius) (Insecta: Hemiptera: Aleyrodidae)”, by Heather J. McAuslane and Hugh A. Smith, was consulted in preparation for this episode of Bug of the Week. Carol Of The Bells by Audionautix is licensed under a Creative Commons Attribution 4.0 license: https://creativecommons.org/licenses/by/4.0/ Artist: http://audionautix.com/

Bug of the Week wishes everyone a joyous, happy, and safe holiday season.

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With winter fast upon us and most deciduous trees and shrubs already naked, my sweet autumn clematis, Clematis terniflora, still shines like a beacon of green as it engulfs a lamppost in the front yard. After rewarding me with fragrant blossoms for much of the fall, this non-native invader is hosting an entire food web of alien insects. Let’s start with the herbivores, a flock of peach-clematis aphids. During spring and summer, through Thanksgiving, and, in this era of climate change perhaps all winter, my clematis will be home to peach-clematis aphids. Several species of clematis and peaches serve as food for this now cosmopolitan vagabond. Beneath each leaf, scores to hundreds of aphids suck nutritious phloem sap. Over the past several months and in years past, the aphid horde is so abundant that clematis leaves drip with honeydew, which in turn serves as a substrate for the growth of sooty mold. This type of non-pathogenic fungus, akin to one produced by boogie woogie aphids and woolly alder aphids we met in previous episodes, blackens leaves and may interfere with photosynthesis.

The saga of the peach-clematis aphids began earlier this year in the spring when winged aphids migrated from a tree in the peach clan (Prunus) to the clematis vine clinging to my lamppost. During the warm months of summer and fall, surviving females begin reproducing without assistance of males. This form of reproduction, called parthenogenesis, produces only females, thus enabling aphid populations to increase rapidly. As I examined my colony of aphids recently, I noticed several winged adults mixed with the parthenogenetic females. In cold regions like Maryland, when temperatures turn chilly, male and female winged adults are produced and leave the clematis, returning to Prunus to mate and lay eggs that will spend the winter on the bark of the tree. Sexual reproduction in the fall produces eggs, the overwintering stage of the aphids. In spring, the eggs hatch and the complex life cycle of the aphid resumes.

Another fact of life contributing to explosive population growth of aphids is their ability to skip the usual insect-like business of laying eggs. Many species of aphids dispense with the egg stage and, like humans, give live birth to their babes. This blessed event takes only a few minutes but appears to be fraught with significant drama. Birthing aphids do lots of posturing and pushing. Fortunately, aphids have sucking mouthparts and loud vocalizations such as those accompanying human births are conspicuously absent. To further accelerate the process of filling the world with their kind, female aphids carry embryos of their grandchildren within their bodies even before they are born (i.e. their daughters are born already pregnant). This further compresses the generation time for aphids and is part of the reason aphid populations rapidly grow from a few to thousands.

With Thanksgiving in the rear view mirror and the rest of Holiday Season just around the corner, peach-clematis aphids are still living it up on sweet autumn clematis. On a leaf blade a mother is surrounded by her daughters, and on a petiole aphids suck sap from phloem. Just for fun, watch the live birth of an aphid (five times actual speed). Note that aphid births are breech. At the end of the clip, is that older sister coming to see how mom and little sister are doing? Dance of the Sugar Plum Fairy by Kevin MacLeod is licensed under a Creative Commons Attribution 4.0 license, https://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100270. Artist: http://incompetech.com/

Just as my clematis serves as a feast for aphids, so too will the aphids and their honeydew serve as dinner for guests higher up the food chain. Roaming around my clematis, multicolored Asian lady beetle larvae snack on aphids. Their alligator-like larvae patrol leaves and stems searching for tasty aphids. Without much stealth or finesse, larvae capture aphids in their jaws and proceeded to munch their hapless prey. Small aphids disappear in just a minute or two, but large, plump aphids required several minutes to eat. A single larva of the multicolored Asian lady beetle may devour 1,200 aphids during the course of development. Adults of this species can also kill hundreds of aphids during their lifetime. This capacity to eat so many aphids makes the multicolored Asian lady beetle one of the most effective biological control agents in our gardens.

In this microcosmic food web, clematis is food for the peach-clematis aphid, and aphids will become food for both adult and larval lady beetles. A yellowjacket laps up carbohydrate rich honeydew produced by the aphids. This rich source of carbohydrates may help yellowjackets fatten up to survive a wicked winter. Dance of the Sugar Plum Fairy by Kevin MacLeod is licensed under a Creative Commons Attribution 4.0 license: https://creativecommons.org/licenses/by/4.0/, Source: http://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100270, Artist: http://incompetech.com/

And during this season of Holiday feasts, what banquet would be complete without dessert? With gobs of sweet honeydew on leaves, dozens of hungry yellowjackets recently visited the clematis to lap up a carbohydrate rich meal to fatten up for their winter rest. So, in this festive season, while we devour turkey and savor pumpkin pie, reflect on the happy feasts underway on greenery like an autumn clematis where aphids dine and serve dinner to other creatures higher up the food web.

Acknowledgements

Bug of the Week thanks Roger Blackman and his amazing website, Aphids on the World’s Plants: An online identification and information guide at http://www.aphidsonworldsplants.info/ which served as a reference for this episode. The fact-filled leaflet “Multicolored Asian Lady Beetle” by Janet Knodel, E. Richard Hoebeke, and Carolyn Klass, Dept. of Entomology, Cornell University provided great information on the ladybeetle. Many thanks to Dr. Gary Miller of USDA’s Systematic Entomology Laboratory for his help in identifying the tiny star of this episode.

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One of the most interesting and charming woody plants in our landscapes is the boxwood. This evergreen shrub has been domesticated by gardeners since the time of the Roman Empire. Pliny wrote about the uses of boxwoods as a garden hedge and as a source of wood for the construction of musical instruments. Boxwoods are featured in the Holiday season in North America and Europe where their glossy, deep green leaves grace wreaths, centerpieces, and garlands in homes. This week on a trip to my favorite market, I passed a boxwood hedge that looked anything but charming. The usually deep green leaves of the boxwood were mottled yellow and orange and disfigured with bumps and blisters. The plants appeared to have a bad case of pox. What misfortune had befallen these noble shrubs? After plucking a few leaves from the embattled boxwoods, and carefully removing the lower surface of a leaf, I discovered several tiny, squirming, yellow maggots just beneath the surface. These were the larvae of the diabolical boxwood leafminer.

The boxwood’s blues began last spring in early May when adult boxwood leafminers emerged from leaves, exiting their leafy nursery. On the way out, the adult flies left behind the shed skin of their former pupal case. The papery skins, called exuviae, protrude from the bottom surface of the leaf for many days before dropping from the plant. Adult boxwood leafminers are delicate orange flies closely resembling mosquitoes. After mating, the female fly seeks the undersurface of a young boxwood leaf. Using a small drill-like structure at the tip of her abdomen, she punches a tiny hole in the surface and lays eggs in the soft tissue beneath. From these eggs tiny yellow boxwood leafminer larvae hatch. During summer and autumn, as the larvae grow, boxwood leaves produce small circles of cells surrounding developing larvae. These cells serve as a source of food for the maggots and produce abnormal swellings of the leaf, called galls. Development slows during the chilly months of winter and early spring, but by April, with the return of warmer temperatures, larvae grow rapidly as the boxwood ramps-up its activity. To escape the protected confines of its mine, the leafminer has a clever trick. Just before pupating, the maggot moves to the lower surface of the leaf and carefully removes almost all of the leaf tissue until only a thin layer is left. This layer forms a window that will be used by the pupa as an escape hatch. With a successful exit strategy in place, the larva pupates and in a few short weeks the pupa pushes through the window, enabling the adult fly to escape.

Peeling back the lower epidermis of a boxwood leaf reveals boxwood leafminer maggots nestled within, ready for a long winter’s nap. Fast forward to next spring, when larvae have completed development and pupated. As they emerge from leaves, shed pupal cases mark the exit sites of adult midges. With jazzy twisting motions, the rockin’ female drills into a tender new leaf to deposit eggs.

Managing leafminers

If you are troubled by boxwood leafminers, then a good, non-insecticidal way to thwart this uninvited guest is to plant varieties of boxwoods resistant to attack by this fiend. Years ago, we discovered that a variety of boxwood from the highlands of Macedonia was highly resistant to the boxwood leafminer. This variety is called Buxus sempervirens ‘Vardar Valley’. You can find it in several nurseries in the DMV. Here’s hoping your boxwoods don’t suffer holiday blues courtesy of the boxwood leafminer.

References

A wealth of information on boxwoods can be found in Lynn Batdorf’s wonderful “Boxwood Handbook”, used as a reference for this story. Information on resistant boxwood varieties came from the article entitled “Integrated approaches for managing the boxwood leafminer, Monarthropalpus flavus” by M.J. Raupp, I.H. Mars, and G. d’Eustachio, the abstract of which can be found at this link:  https://www.actahort.org/members/showpdf?booknrarnr=630_6

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