Eleodes stands on its head as a warning to predators. Warning ignored? Get ready for a stinky stinging dose of noxious chemicals from the beetle’s rear end.
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.
Check out the stinky discharge that issued from the beetle’s rear end when disturbed by a bug geek.
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 picture has little to do with the story other than to remind us of the beauty of the desert and our national parks.
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.
Bracket fungi are the stage for romance and rivalry of forked fungus beetles. Photo by Cathy Keifer
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.
Male forked fungus beetles use large upper horns and smaller lower horns to battle for possession of their mate. Photo by Cathy Keifer
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
Lovely female beetles lack the prominent horns of their male suitors. Photo by Cathy Keifer
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:
Pillbugs are crustaceans and more closely related to crabs than to insects. They play an important role as recyclers of organic matter. Image credit: Paula Shrewsbury, PhD
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.
The ability to roll into a tight ball resembling a pill gives pillbugs their name.
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.
But a few millimeters in length, tiny, handsome carpet beetles sometimes appear in my home on wintry days.
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.
Hairs on dermestid larvae can cause dermatitis to some people.
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.
Uh oh, ragged holes in my woolen cap look like the handiwork of carpet beetles.
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.
An untidy pile of frass behind a dead insect specimen is a sure indication of a dermestid beetle infestation.
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:
And what to my wondering eyes should appear, but a colony of whiteflies, bringing holiday cheer.
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.
Yellow patches on poinsettia leaves may be a sign of whiteflies feeding below.
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.
Droplets of sweet sticky honeydew are produced as a waste product when whiteflies feed.
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!
Despite some chilly weather, peach-clematis aphids keep on keeping on the leaves of my sweet autumn clematis.
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.
No ho ho ho for this boxwood leaf loaded with larvae of boxwood leafminer.
Glossy, dark green leaves of a healthy boxwood are conspicuously absent when infestations of boxwood leafminer give boxwoods a bad case of the blues.
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
Sparkling scales of brown, black, and silver give the Indian meal moth a rather comely appearance.
Holiday season is baking season. Pies, cookies, cakes, and breads are comfort foods many crave on chilly days. During this season of culinary delight, cupboards and pantries receive lots of attention and activity. On a recent socially-distanced visit to a friend’s home, we noticed tiny moths flitting about the kitchen. A peek inside the pantry revealed more than a minor swarm of said moths. During this holiday season, many hopeful bakers will open pantries and be greeted by clouds of these small wonders, a cosmopolitan raider of the pantry, the Indian meal moth, Plodia interpunctella. While fascinating for entomologists, this is an unwelcome surprise for most folks.
Silk inside plastic bags or containers is a pretty sure sign of a meal moth infestation.
The adult stage of this insect is a rather small moth just slightly larger than ½ inch in length, with wings banded white and rusty red. They flit about the pantry or cupboard in search of mates and tasty products rich in carbohydrates, fats, and proteins. One recent infestation in my cupboard raged in a package of organic cashews. Within the package, small cream colored caterpillars spun silken webs and sallied forth to consume the nutritious nuts. In addition to spinning silken galleries, larvae deposited frass, the digested remains of their meal. The voided frass was entangled in silken strands to form a nasty messy web. Two excellent clues signaling the presence of meal moths are the presence of silk and frass within a bag of flour, grain, seeds, or pet food. After larvae complete development, they may gnaw holes and escape their plastic prisons. Nomadic caterpillars are often found wandering about the walls and ceiling of the pantry in search of a protected spot to spin cocoons and develop into pupae. Sometimes vagabond larvae enter cracks between shelves, lids of jars, electrical sockets, or seams behind baseboards to pupate. Soon the next generation of adults will appear, intent on finding new bags and boxes of stored products to infest.
Within a plastic bag, scads of meal moth caterpillars spin silken webs and deposit frass while devouring my once tasty organically grown cashews. While caterpillars are a rich source of protein, this much extra protein with my nuts I don’t need.
How do meal moths colonize pantries in the first place? It is possible that original infestations of meal moths arrive with cereal, seeds, dried fruit, or grain as a few tiny eggs within a package from the store. After hatching from eggs, small caterpillars in a bag of seeds in the back of a closet could go unnoticed, but this vanguard is capable of generating sufficient moths to initiate a full blown mothagedon. Meal moths also survive outdoors and are commonly found in caches of nuts or seeds stored by squirrels or rodents. Adult moths originating outdoors can invade indoor pantries during warm weather when doors and windows are wide open. Mice often enter homes in autumn and winter seeking shelter and bringing stockpiles of seeds with them. These seeds might arrive contaminated with the associated moth eggs and may become a source of infestations indoors.
Indian meal moth caterpillars can chew through plastic and invade other bags of grain, seeds, and fruit.
What should you do if you find these rascals in a pantry or cupboard? First, remove all goods and products from the storage area. Vacuum the cupboard, pantry, or cabinet like there is no tomorrow. Carefully inspect all cracks, corners, crevices, and seams in the cupboard and remove any larvae or pupae you find. Seal as many of these refuges as possible with caulk. Remove and replace loose paper used to line shelves. Inspect any pots, pans, glasses or other items occupying the pantry where food will be stored and remove any meal moths on these items as well. Inspect opened and unopened bags and boxes of food for signs of silk, frass, larvae, or moths. If in doubt, toss it out. My pantry pest guru recommends the “deep chill” treatment for unopened packages you might want to salvage, but are suspect by association. Place unopened bags in the freezer for one week, remove them for one week, and then freeze again for a final week. The intermittent week of thaw tricks eggs into hatching and the tiny caterpillars are then killed by the second trip to subzero land. When you purchase items that might serve as food for meal moths, seal them in strong plastic storage containers with tightly fitting lids. This will help prevent any moths you might have missed during the crusade from laying eggs that hatch into larvae capable of infesting your food. Try not to store prime foods like grain or dried fruit for very long periods of time. The longer stored products remain on a shelf, the more likely they are to be infested by an itinerant moth that happens by.
Pheromone traps can be used to capture male meal moths and gage their activity and numbers.
One approach useful in alerting you to an incipient invasion of meal moths is to purchase and deploy pheromone traps. These small triangular boxes are placed inside your pantry or cupboard. Inside the box is a sex pheromone bait that attracts the male meal moth from many feet away. The ever-hopeful male senses the pheromone, a chemical signal released by a female, and is tricked into believing that a receptive beauty waits inside the open-ended trap. He flies inside to find his mate, but instead becomes ensnared by a sticky substance lining the inside of the trap. By placing these traps within a pantry, you can detect the emergence of male moths that may be the harbingers of a burgeoning population of moths in your cupboard. This advanced warning serves as a signal to initiate a search and destroy mission. Good luck hunting moths and protecting your baking supplies during this season of culinary delight.
Acknowledgements
We thank Linda and Jeff for sharing their relentless Indian meal moths with Bug of the Week and Dr. Nancy Breisch for the wealth of information and advice about bugs. The Handbook of Pest Control, Ninth Edition, by Arnold Mallis was used as a resource.
Fruit flies like this African fig fly may join Thanksgiving festivities in your home. Photo credit: Maggie Lewis
Just before Thanksgiving kicks off the holiday season, scads of questions show up in my mailbox about hordes of tiny flies buzzing around fruit bowls, kitchen sinks, and counters tops. They seem to appear from nowhere and lend credence to Aristotle’s notion of spontaneous generation, the theory that living organisms like flies somehow originate spontaneously from non-living or putrefying things. To help untangle this mystery, consider the change of seasons. Late autumn in the DMV and many other parts of our land is characterized by cool damp weather. Moist evenings and mornings punctuated by warmish days are nearly ideal for decomposing tons of leaves, fruits, and other vegetable matter, the accumulated bounty of Mother Nature’s efforts during spring and summer. This week of Thanksgiving, my compost pile is a writhing mass of invertebrates intent on converting vegetable protein into animal biomass as quickly as possible. On warm days, a cloud of fruit flies hovers over my compost and some of these winged raiders undoubtedly infiltrate my home when doors open.
Like many kitchens, mine is home to a bowl of fruit that occasionally contains one item gone a little squidgy. Yeasty odors of acetic acid and ethanol emanating from an over-ripe banana serve as powerful attractants for fruit flies. After arriving at a slightly brown banana, the female fruit fly deposits eggs. Each gal lays roughly 500 eggs during the course of her life time. Small translucent larvae hatch from the eggs. They glide through the overripe fruit slurping-up nutritious fermenting fluids as they develop and grow. With warm ambient temperatures, fruit flies can complete a generation in less than two weeks. With their capacity for reproduction, populations around the fruit bowl can explode seemingly overnight. One careless week, I neglected to empty the stainless steel compost bin on my kitchen counter and I was rewarded with several hundred fruit fly maggots happily growing in the bin. Yikes!
Dozens of fruit flies could not escape the irresistible odors of vinegar. Once inside the jar, a perforated plastic cover prevented escape and sealed their fate. Photo credit: Ingalisa Schrobsdorff
Fruit flies can also enter home as stowaways with overripe fruits or vegetables from the market or garden. These goods may arrive preloaded with a complement of eggs or tiny larvae. To reduce chances of bringing home an infestation, inspect your produce carefully and wash fruits or vegetables before you set them out in a bowl. If fruit is unrefrigerated and displayed in a bowl, check it out regularly and toss over-the-hill items before they generate flies. Fruit flies often breed in sink or floor drains, garbage pails, or recycling containers in homes, restaurants, and offices where decomposing organic material accumulates. Inspect these areas regularly, clean up spills, and disinfect surfaces. For the cloud of fruit flies wafting around your home, consider building a vinegar trap to catch and kill these noisome rascals. Traps can be purchased commercially and several trap designs are available on the internet. My do-it-yourself vinegar trap consists of an 8 oz. clear plastic tumbler filled with 4 oz. of apple cider vinegar or wine vinegar and a few drops of dish detergent. Within 24 hours of placing the trap on the counter, more than 100 fruit flies were lured to their death. One clever modification of the trap includes fastening a bit of plastic wrap over the lid of the vessel with rubber bands a poking a few holes in the plastic. Apparently, this allows fruit flies to enter but confounds attempts to escape should they change their tiny minds about a vinegary death by drowning.
More than just an indoor nuisance, several invasive species of fruit flies have now established in our region. The spotted-wing drosophila, Drosophila suzukii, first detected in the US in 2008 in California, has now spread from coast to coast and border to border. It is a major pest of strawberries, blueberries, raspberries, black berries, and cherries, and crop losses in the United Sates alone are estimated to exceed hundreds of millions of dollars annually. If spotted-wing drosophila was not enough, a second dastardly fruit fly, the African fig fly, Zaprionus indianus, first detected in Florida in 2005, has now spread to the Canadian border and can also be found here in the DMV. African fig flies infest a broad range of plants, including berry crops as well as figs, grapes, and cherries. Unlike spotted-wing drosophila, female African fig flies generally cannot cut through intact fruit skin to lay eggs; they instead are thought to oviposit (deposit eggs) into or near pre-existing cracks and wounds. In some varieties of grapes, the African fig fly may actually out-compete its Asian relative, the spotted-wing drosophila.
African fig fly is an invasive fruit fly species that was first detected in the United States in 2005 and has since established in Maryland. Adults can be identified by the white and black stripes running longitudinally down their back. While spotting an adult is easy, spotting a larva swimming in a raspberry is a bit harder and somewhat disconcerting if the raspberry is in your cereal. Video credit: Maggie Lewis
African fig fly eggs are strange things with several long filaments at one end. These filaments help the egg obtain oxygen. Photo credit: Maggie Lewis
Ah, but fruit flies are not all bad. The most famous fruit fly of all is, of course, Drosophila melanogaster. This tiny workhorse of scientific studies, a hero many of us met for the first time in high school biology, brought the 1933 Nobel Prize in Physiology or Medicine to Thomas Hunt Morgan for his pioneering work on mechanisms of heredity and the location of genes on chromosomes. Fruit flies have ventured to the International Space Station to help scientists study the effects of zero gravity on cardiac function and immune responses to disease. Closer to home and in my compost bin, they provide a vital ecological service by unlocking nutrients tied up in vegetable waste and returning these nutrients to food webs. So for good or bad, hail the tiny but mighty fruit fly.
On this unprecedented Thanksgiving in the time of COVID-19, Bug of the Week wishes you a happy one. Be sure to share some of your unwanted vegetables with ever-grateful fruit flies in your compost!
References
The wonderful video, images, and ideas for this week’s episode were created by doctoral candidate Maggie Lewis of the Department of Entomology, University of Maryland, College Park. We thank Ingalisa and Sahar Schrobsdorff for providing inspiration for this story and sharing an image of their clever fruit fly trap. The interesting references “Trapping spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), with combinations of vinegar and wine, and acetic acid and ethanol” by P. J. Landolt, T. Adams, and H. Rogg, “Spotted Wing Drosophila: Potential Economic Impact of a Newly Established Pest” by M. Bolda, R. Goodhue, and F. Zalom, “Effects of Interspecific Larval Competition on Developmental Parameters in Nutrient Sources Between Drosophila suzukii (Diptera: Drosophilidae) and Zaprionus indianus” by M. Edana Shrader, H. J. Burrack, and D. G. Pfeiffer, and “Flies, gnats, and midges” by W. A. Kolbe in “The Handbook of Pest Control” were used in preparing this Bug of the Week. To learn more about the African fig fly, please visit the following website: https://academic.oup.com/jipm/article/10/1/20/5514212#136729274
Twisted gnarly leaves on my pretty Nyssa are the handiwork of a tiny gall-making insect.
The range of color in Nyssa’s autumn display is hard to beat.
Some call it tupelo, others call it black or sour gum, but I call it drop-dead gorgeous, Nyssa sylvatica. Of all the trees in the forest, I think this one takes home first prize in autumn with shades of scarlet, orange, yellow, and green swirled together in a raucous mix. A common native of eastern North American forests, this beauty is almost pest free and thrives in managed landscapes.
One summer’s day while enjoying my Nyssa’s deep glossy leaves, I was miffed by several gnarly leaves at the tips of branches. Along the margins of said leaves were numerous yellowish-white crescent shaped galls. Galls are abnormal plant growths often associated with an insect, mite, nematode, or microbial pathogen. To get a closer look at this aberration, I plucked a few leaves and dissected the galls under the lens of a powerful microscope. The galls were hollow pockets packed with hordes of tiny yellow sucking insects known as phylloxerids, close kin to woolly aphids we met on beech trees and alder branches. These suckers are tiny, about a millimeter in length. Within each gall several of these gals were surrounded by dozens of pill-shaped translucent eggs, offspring produced asexually, without contributions from males.
Early in the growing season, phylloxerids induce small crescent-shaped galls along the margins of leaves.
How do they make galls? Well, galls form when an invading biotic agent, in this case a tiny insect, takes control of the genetic machinery of the undifferentiated cells in the developing leaf. Compounds released by the insect as it feeds tell the cells of the leaf something like this, “don’t expand to form a normal flat leaf, curl over along the margin and form a nice hollow pocket, a home where I can lay eggs and my children and I can dine unseen and unmolested by hungry predators.” How clever is that! Pretty clever indeed, but one small problem exists. During autumn when my Nyssa drops its gnarly leaves, surely these leaf-bound gall-dwellers do not fare well in the soil. Where do the tiny phylloxerids go?
Early in the season, marginal galls created the phylloxerid twist and distort young leaves at the tips of Nyssa’s branches. Within each gall are female phylloxerids laying dozens of pill-shaped eggs. Phylloxerids are strange looking creatures. Between the first set of legs in the center of the body are sucking mouthparts used to initiate gall formation and to remove sap from the leaf’s cells.
Up in the treetop, flocculant tufts of wax mark the location of tiny insects. Are these overwintering phylloxerids that will lay claim to my Nyssa next spring?
In a remarkable treatise on all things phylloxerid published some 116 years ago, Theo Pergande of Cornell University described the overwintering stages of the phylloxerid. He observed tiny wax covered phylloxerids in protected locations on the bark of the Nyssa. This week I scaled my Nyssa and several meters up in craggy folds along the trunk and in rough patches of bark were small white tufts of wax housing tiny sucking insects, presumably the overwintering generation of phylloxerids. While the exact molecular mechanisms by which gall-makers control their plant-hosts remain largely unknown, hundreds of species of insects and mites have discovered astonishing ways to alter the plants they live on and in during millions of years of intimate association.
Acknowledgements
We thank Drs. Fredericka Hamilton and Gary Miller of USDA for help in identifying the tiny creature featured in this episode. “North American Phylloxerinae Affecting Hicoria (Carya) and Other Trees” by Theo Pergande, and the amazing ‘Aphids on Worlds Plants’ website were used as references for this episode.
