Beleaguered boxwoods beware, box tree moth, Cydalima perspectalis, arrives in the DMV

There is no mistaking this caterpillar on a boxwood. This is the larva of the box tree moth. Paula Shrewsbury image

From the time of our earliest European colonists, boxwoods have been important components of ornamental landscapes. Boxwoods grace iconic landscapes in the DMV including George Washington’s home at Mount Vernon, the “Box Walk” at  Dumbarton Oaks,  the National Boxwood Collection at the United States National Arboretum, as well as hundreds of public and private gardens and landscapes in our region. However, boxwoods are one of the most problem-prone plants in our landscapes. Already beset by exotic pests including leafminers, spider mites, and pathogens such as boxwood blight, boxwoods in the DMV and throughout our country now face a new, lethal non-native invader, the box tree moth.  Like many of our new invaders box tree moth is native to Asia in China, Japan, and Korea. Probably due to the movement of ornamental plants, it entered Europe and was first discovered in Germany in 2007. It now occupies more than 30 Eurasian countries. It jumped across the Atlantic to Canada where it was detected in 2018 and arrived in the United States with shipments of nursery plants from Canada in 2020 and 2021. Prior to July, 2025 it spread to Delaware, Massachusetts, Michigan, Ohio, Pennsylvania, West Virginia, and New York. Yes, the DMV was surrounded and sure enough, it was detected in Clarke and Loudoun Counties in Virginia and three locations in Washington County in Maryland during the latter half of July and early August.

Iconic boxwoods are one of the most widely planted shrubs throughout the country and here in the DMV. Beset by pests like leafminers, spider mites, and boxwood blight, they now have a devastating new enemy, the box tree moth. Caterpillars of box tree moth defoliated these once handsome boxwoods. The shrubs will be destroyed in hopes of slowing the spread of the moth. Watch as hordes of caterpillars consume foliage until only midveins and silken webs laced with nasty frass remain. In addition to destroying the boxwoods, these miserable leaf-munchers will sometimes eat each other. If your boxwood looks like this, and you see these, please contact your state department of agriculture or university extension service.

What’s the worry? If undetected, an infested boxwood can support a rapidly expanding population of leaf-eating caterpillars capable of completely defoliating large boxwoods. In addition, they create large silken webs littered with frass that accumulates on plants and on surfaces below.

How is this possible? Adult boxwood tree moths lay multiple clutches of 5 to 20 eggs. Larvae that hatch from the eggs are voracious herbivores that first remove green leaf tissue as youngsters and later consume entire leaves. And if this was not bad enough, after leaves are consumed, they feed on woody tissues thereby girdling stems and branches, hastening boxwood death. One generation of this carnage is bad enough, but box tree moth will have many generations in the DMV. In other locations, as many as 4 or 5  generations may occur annually depending on temperature regimes.

What should you look for? Discoloration, a change in the color of leaves from vibrant green to dull brown or gray and defoliation, the loss of parts or entire leaves are often the first and most easily recognizable clues that your boxwoods may be infested with box tree moth. Since no native moth or butterfly has caterpillars that readily eat leaves of boxwoods, the presence of large numbers of strikingly colored black, green, and yellow striped caterpillars with black heads is a dead giveaway for the presence of box tree moths. However, several other arthropod pests and diseases can cause discoloration, defoliation, and dieback on boxwoods. Fortunately, Joe Boggs of The Ohio State University has complied a wonderful pictorial guide to diagnosing boxwood pests and diseases including symptoms and signs of box tree moth.

Defoliated leaves covered with silk and hordes of caterpillars decked out in stripes and spots of green, yellow, white, and black with shiny jet-black heads mark an infestation of box tree moth caterpillars. Paula Shrewsbury image

What should you do if you find box tree moth? The Maryland Department of Agriculture is presently engaged in a program to limit the spread of box tree moth. If you suspect you have this pest, the Department of Agriculture recommends the following:

·         If you suspect your boxwoods may be infested with the box tree moth, please contact via email the Plant Protection and Weed Management program at [email protected]. Please attach a picture in your email.

·         Allow Maryland or Federal agricultural officials to inspect your boxwood plants and place detection traps.

·         Any infested material should be doubled bagged in plastic bags and placed in the trash.

·         Nursery owners should monitor their boxwoods and implement safeguards to limit pest risk. All licensed nurseries should report BTM detections to the Maryland Dept of Agriculture Nursery Inspection Program or reach out to their nursery inspector.

Moving forward, what might the future hold for the box tree moth and us? Unfortunately, like emerald ash borers, brown marmorated stink bugs, spotted lanternflies and many other non-native pests of our landscape plants, the box tree moth is likely here to stay. However, Mother Nature in cooperation with humans often has a solution for these invaders. Indigenous natural enemies, predators, parasitoids, and pathogens often rally and put a beat-down on these non-native pests. Clever scientists search and discover natural enemies from afar and after exhaustive evaluation release them to reduce populations of invaders here in the US. Researchers develop chemicals to detect, attract, trap, and kill non-native pests. Even today several insecticides are available to kill caterpillars. Some of these contain active ingredients like Bacillus thuringiensis, a.k.a. BT, and spinosad which are dynamite for controlling caterpillars but safe enough to be used in organic food production.  If you want to learn more about insecticides that can be used to manage box tree moth caterpillars, click on this link. With diligence, ingenuity, good science, and help from Mother Nature, we will find ways to manage this new  noxious invader.  

Box tree moth caterpillars can destroy an established stand of boxwoods like this one in a matter of weeks. Joe Boggs, OSU.

References and acknowledgements

“The fast invasion of Europe by the box tree moth: an additional example coupling multiple introduction events, bridgehead effects and admixture events” by Audrey Bras, Eric Lombaert, Marc Kenis, Hongmei Li, Alexis Bernard, Jérôme Rousselet, Alain Roques, and Marie‑Anne Auger‑Rozenberg was used as a reference for this episode. We thank Joe Boggs for generously allowing us to use his wonderful images of box tree moth. The inspiration for this episode came from Phyllis and Rod who allowed us to photograph their boxwoods and caterpillars.  Please visit Box Tree Moth by Madeline Potter to learn more about this pest and explore links to additional information.

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Five years ago in an episode entitled “Missing bugs of the week: Swallowtail butterflies, Papilionidae” we explored some of the reasons pollinators in general and butterflies in particular are imperiled in the DMV and around the world. Last month a concerned nature enthusiast remarked “normally by this time of the year our meadow would be full of butterflies… even a monarch or two…. This year there’s virtually none and I hear it’s that way throughout the county.” In a sample size of one, in my own flower garden in Columbia, MD, thus far this season it has been a rotten one for large butterflies like swallowtails and monarchs that usually are plentiful by now.  My barometer for gauging butterfly abundance is a large native composite known as cup plant (Silphium perfoliatum). In years past during the last weeks of July and first weeks of August, I have seen more than a dozen swallowtails simultaneously enjoying nectar treats on my cup plant. To date only a single tiger swallowtail has visited my cup plant. How disappointing is that?  

Over the last few weeks, folks expressed concern over the absence of swallowtail butterflies in their gardens and meadows. I’ve had the same impression. This video from 2019 shows dozens of tiger swallowtails visiting my cup plant in late July. Fast forward to the same time this year when only a single tiger swallowtail has stopped by. Is this just annual variation in weather conditions or signs of larger issues related to climate change, development, and other sources of butterfly decline? Maybe missing butterflies is just a local suburban thing. Earlier this year on the banks of the Potomac, zebra swallowtails, tiger swallowtails, and other swallowtail species were common gathering minerals from the mud. And in my gardens skippers and cabbage butterflies showed up in force right on time. I’m not really sure what’s up with the swallowtails but I hope a second generation of swallowtails and maybe some monarchs make an appearance soon.

How are butterflies fairing around the country? A recent article in the Proceedings of the National Academy of Sciences  provides some clues as to why butterflies and other pollinators are becoming harder to see and why they may be declining in the United States and Canada. Tara Cornelisse and 14 colleagues found that roughly 26% of vertebrate and invertebrate pollinators are at risk of extinction in North America north of Mexico. When it comes to butterflies, of the 632 butterfly species studied, almost 20% are at risk of extinction. Of these approximately 8% of charismatic swallowtails are at risk. Yikes!

What are the underlying ecological threats to pollinators in general and butterflies specifically? We have known for decades that changes in land use patterns associated with urbanization around the world are responsible for dramatic losses of several insect species, including butterflies. In addition to urban development, the study by Cornelisse et al. ranked climate change, invasive species, changes in the natural patterns of water movement and storage, and changes in wildfire regimes as key risk factors for butterflies and moths. On a national level pollution also imperiled all pollinators in several eastern states.   

Findings of this study send a warning regarding the overall fate of pollinators in our rapidly changing world. However, declines in the abundance of butterflies from one year to the next are often linked to more immediate ecological events such as annual variation in weather. Elevated temperatures are known to reduce the survival of caterpillars. Drought is known to reduce the abundance and nutritional quality of some plants. One butterfly expert suggested that last summer’s extended heat and drought may have negatively affected the survival of butterfly larvae, thereby reducing the populations of butterflies in 2025. Perhaps, our unusually soggy spring weather favored pathogens lethal to butterfly larvae or pupae.

Should we fear that the apparent scarcity of swallowtails in 2025 in my garden in Columbia portends a pending butterfly apocalypse? Maybe not. Beyond swallowtails, other species of butterflies like silver spotted skippers and their kin arrived in my garden right on schedule in fine numbers, as did cabbage butterflies. Recent adventures along the C & O Canal this spring and summer revealed several species of butterflies including tiger and zebra swallowtails in good numbers. Rick Borchelt’s butterfly surveys in Allegany and Kent Counties in Maryland revealed solid numbers of dozens of butterfly species. But as I finish writing this episode and look out the window to the cup plant, swallowtails are still absent. However, hope springs eternal in the hearts of bug geeks and maybe an upcoming brood of swallowtails and some late-to-arrive monarchs will stop by garden my before the summer ends.

Acknowledgements

Bug of the Week thanks Paul Bade for his interest in swallowtails that provided the inspiration for this episode. Science writer, butterfly guru, and keeper of the LepLog Rick Borchelt provided great insights and observations of butterflies throughout the region. Many thanks to colleagues in the Department of Entomology, especially Karin Burghardt and Leo Shapiro for providing references and helping clarify several points discussed in this episode. The following fascinating papers were consulted: “Live fast, die young? Day- and night-warming affect the growth, survivorship, and behavior of caterpillars in the field” by Louie H. Yang, Elizabeth G. Postema, Heran Arefaine, Fernanda Y. Cohoon, Emma A. Deen, Yvonne L. Durand, Gwendolyn I. Erdosh, Hailey Ma, Courtney N. Mausling, Sarah Solís, and Madeline R. Wilson,   “Western Monarch Population Plummets: Status, Probable Causes, and Recommended Conservation Actions” by Emma M. Pelton, Cheryl B. Schultz, Sarina J. Jepsen, Scott Hoffman Black and Elizabeth E. Crone; “Multiscale seasonal factors drive the size of winter monarch colonies” by Sarah P. Saunders, Leslie Ries, Naresh Neupane, M. Isabel Ramírez, Eligio García-Serrano, Eduardo Rendón-Salinas, and Elise F. Zipkina; “Declines and Resilience of Communities of Leaf Chewing Insects on Missouri Oaks Following Spring Frost and Summer Drought” by Robert J. Marquis, John T. Lill, Rebecca E. Forkner, Josiane Le Corff, John M. Landosky and James B. Whitfield; and “Elevated extinction risk in over one-fifth of native North American pollinators” by Tara Cornelisse, David W. Inouye, Rebecca E. Irwin, Sarina Jepsen, Jonathan R. Mawdsley, Margaret Ormes, Jaret Daniels, Diane M. Debinski, Terry Griswold, John Klymko , Michael C. Orr, Leif Richardson, Nicole Sears, Dale Schweitzer, and Bruce E. Young.

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One of my favorite mythological tales is that of King Midas, the ruler of Phrygia who wished for and was granted the power to turn everything he touched into gold. Apparently, this was his undoing as he starved to death when the food he touched turned into inedible gold – poor guy. Last week my nature- loving neighbor shared a wonderful video of majestic mydas flies cavorting around the stump of an ancient pin oak tree that once graced her yard. It seems this stump serves as a perennial home for her mydas flies. Each summer they provide entertaining performances as males battle each other and find romance with the females which, in turn, search for places to deposit their spawn in just the right spot in the decaying stump. Female mydas flies deposit eggs in rotting wood where their predaceous larvae dine on other soft bodied insects, including the grubs of scarab beetles, kin of the ones we met in previous episodes such as “Hercules Beetles.”

The star of this episode, Mydas clavatus, the clubbed mydas fly, named for its clubbed antennae, is a member of a relatively small family of very large flies whose biology remains somewhat unknown. Mydas clavatus is among the largest of all North American flies, with a body length often more than an inch. It is believed that their black–velvet coloration presents the visage of a large stinging wasp. This confers protection from enlightened predators that have learned not to mess with painful, black, stinging insects. One report holds that they also have a behavioral mimicry in which they curl their abdomen and jab at an aggressor in a mock stinging charade aimed to fool potential predators.

Decaying stumps like this one serve as a home for scarab grubs, a critical food source for mydas fly larvae. Watch as a mydas fly searches the base of the stump. Maybe it’s a female looking for just the right spot to deposit her eggs. Nearby on leaves of a holly a mydas fly does a little fly dance with its forelegs.  And on a lilac near the stump another mydas fly shows no fear of a bug geek with a camera. Video credits to Pam Gealy and Michael Raupp

Adult flies have been observed dining on the nectar and pollen of flowers of Spiraea alba, Pycnanthemum virginianum, Asclepias syriaca, A. verticillata, Monarda punctata, Teucrium canadense, Verbena hastata and Saponana officinali. In years past, they frequented by garden, attracted perhaps by the abundance of butterfly weed in my flower bed which served as a beacon for this unusual visitor.

Adult mydas flies are rather tranquil and allow bug geeks to take pictures before flying away for some unknown fly business. Unfortunately for me, the mydas fly that have visited my garden for photo ops lacked the Midas touch and the holly and pumpkin on which it perched failed to turn to gold. Still, seeing these unusual creatures always provides a golden moment for a bug geek.

References

Bug of the Week thanks Pam Gealey for sharing videos and images of her majestic mydas flies that inspired with episode. Dr. Shrewsbury captured images of the mydas fly. The delightful account “Adult female Mydas clavatus (Diptera: Mydidae) feeding on flowers in Wisconsin” by Andrew H. Williams and the interesting web page “Mydas fly” by Jeffrey K. Barnes were used as references.

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In previous episodes we visited sensational Asian giant hornets, a.k.a. murder hornets, and some of their look-alikes including European hornets and cicada killer wasps. Last week I received an inquiry about male cicada killers. A curious homeowner wondered if they were harmful to humans. This week we revisit an episode from a few years ago to learn about these amazing aerial acrobats. Sit back and relax, male cicada killers are harmless to humans but female cicada killers are lethal to annual cicadas. Female cicada killers kill cicadas as a food source for their young. During the daytime, female cicada killers hunt prey in the treetops where annual cicadas are found. Once captured and paralyzed, cicadas are interred in subterranean crypts. To see how female cicada killers roll, please check out this episode of Bug of the Week, “Cicadas beware, the ladies are in town: Female cicada killer, Sphecius speciosus”.

Although they appear fierce and perhaps even dangerous, male cicada killers pose no threat to humans or pets. Only females have a stinger, and try as he might, the male’s jaws and genitalia failed to puncture my skin. However, I have heard tales of females delivering a memorable defensive sting when inadvertently stepped on or trapped under knee or hand. Video credit: Paula Shrewsbury, UMD

But in advance of the appearance of the ladies, two male cicada killers established territories about twenty feet apart in my flower bed. So began a fierce competition for dominance of space and, I suppose, eventual access to the babes soon to emerge from the earth. Each morning shortly after sunrise as the morning sun warms the land, two feisty males arrive at their respective perches, one on a short yew bush and the other on the nozzle of my garden hose. As you will see in the video, they are on high alert, frequently leaving their perch for a short flight. Not quite understanding the thinking of the wasp mind, I imagine these forays are designed to provoke a battle with the other hopeful suitor. Occasionally, these sorties extend far enough from the perch that one male will enter the territory of the other. This results in a remarkable battle complete with frenetic buzzing and males interlocked in flight. It appears much biting and kicking goes on as evidenced by the response of a cicada killer when I captured one and held it. Eventually one breaks away and skedaddles toward my neighbor’s lawn with the victor in hot pursuit. But the victory seems fleeting. Male cicada killers either have remarkably short memories or indefatigable egos as the aftermath of these vicious mêlées soon results in both males returning to their perches only to repeat the battle a short time later.

One perched on a shrub, the other perched on my garden hose. These two fellows are pumped and looking for a tussle.  Short forays from the perch sometimes result in spectacular aerial battles as each tries to lay claim to the territory where females will soon appear.  Video credit: M. J. Raupp

Perhaps one sunny morning only one of these fierce flyers will remain and the vanquished will have departed for less ardently defended turf in search of his own mate.  But for now, with coffee in hand, this is the best early morning bug show in my garden.     

Acknowledgements

For more information about cicada killers including videos of them in action, please visit Chuck Holliday’s magnificent cicada killer website, BIOLOGY OF CICADA KILLER WASPS.

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For the better part of the last moth inquiries about spotted lanternflies have poured into my mailbox. One of the most interesting dealt with the appearance of a remarkable “albino” lanternfly spotted by an inquisitive citizen. Albinism in humans and other animals results when cells responsible for producing melanin, a pigment responsible for color of skin, hair, and eyes, fail to produce enough melanin.  While relatively common in humans and other vertebrates, albinism is rare in insects. The pale orange spotted lanternfly that inspired this story is likely a recently molted fourth instar lanternfly nymph.  Time out, what the heck does that mean? Lanternflies belong to a clan of insects called the Hemiptera. These insects have sucking mouthparts to sip plant fluids.  Their development includes three life stages, eggs, nymphs, and adults. From spotted lanternfly eggs hatch polka-dotted black and white juveniles called first instar nymphs. As they grow from one stage to the next, they shed their exoskeleton just like our more familiar blue crab. Once they shed their old skin, they are almost pure white for a while as their new skin hardens and begins to develop color. The second and third instar nymphs are also black with white spots. However, the last nymphal stage, the fourth instar nymph, is bright red with black patches and white spots when its pigmentation is complete. The picture that inspired this episode is a newly molted fourth instar nymph in the process of turning from pale orange to brilliant red.

Last May in the DMV spotted lanternfly nymphs hatched from eggs. Newly hatched lanternflies are pure white and appear to be albino, but soon they turn jet black and are speckled with white polka dots. For months they have been feeding on leaves and stems of plants in landscapes and gardens. But a few weeks ago, we began to see the beautiful fourth instar nymphs, their scarlet bodies covered with black patches and white spots. Last week reports of adult lanternflies streamed in as lanternflies landed on people and walked across windshields of cars. It won’t be long before hordes of lanternflies gather on trees, shrubs, and vines to feed.   So, get ready DMV, here come the lanternflies.   

The most frequently asked question in the Bug of the Week mailbag over the past two weeks is why are we seeing so many spotted lanternflies? At least three reasons help us understand why this is the case. First, let’s go back a decade or so to spotted lanternflies’ original detection in Berks County, PA.  In the intervening decade, spotted lanternflies have established and are reproducing in more than fifteen states. They have spread more than 600 miles away from ground zero in Berks County. More people are encountering lanternflies simply because they now occupy a much larger geographic area in the US. Here in the DMV we have gone from a few infested counties in Maryland and Virginia in 2018, to more than 60 infested counties. Yes, folks lanternflies are also in the District of Columbia.

Second, as lanternflies spread either by natural means or with assistance from humans, new colonies are established. These new infestations often are founded by an egg mass or two, each with 30 to 60 eggs, that hitched a ride on lawn furniture, a camper, or maybe a metal sculpture. For several years these pioneers might be off the radar, undetected, as was the case with the initial introduction of spotted lanternflies in Pennsylvania. With abundant food sources like the invasive tree of heaven and other delectable plants and low levels of predators, parasites, and pathogens tracking their burgeoning populations, lanternflies can enjoy a period of exponential growth. As satellite colonies merge along the ever-expanding lanternfly front and as populations expand in the generally infested area, more people encounter spotted lanternflies.  

Third, size matters. Bigger insects are more commonly noticed than smaller ones. Tiny lanternfly nymphs hatching from an egg are but a few millimeters long. They scuttle about vegetation on the forest floor and low-lying shrubs feeding on more than 100 plant species. However, by July, brilliant red nymphs have molted into tawny coated adults an inch or more in length. Being more than 20 times larger than their youngsters, adults are more readily noticed as they cluster on the trunks of trees or take flight and move about the landscape in search of food, mates, and places to deposit eggs. In reality, due to the high mortality of juveniles which is the hallmark of most insect species, there are far fewer lanternflies now than there were back in May when eggs first hatched. I’ll bet you are finding little or no solace in this.

You think Superman is faster than a speeding bullet? Just watch this lanternfly nymph jet away from the nosy camera. Watch again at one twentieth of normal speed. That’s one speedy bug.  

What’s next for spotted lanternfly here in the DMV? Hordes of adult lanternflies and their attendant deluge of honeydew soon will coat vegetation underlying lanternfly infested trees. Honeydew is a substrate for the growth of sooty mold, a non-pathogenic mold that cloaks leaves and stems of plants, reducing the ability of plants to capture the energy of sunlight and conduct photosynthesis. More disturbing will be the arrival of sugar junkies, hordes of wasps and bees intent on enjoying the carbohydrate bounty.   

Is there any good news here? As we learned last autumn, scientists at Penn State documented more than 1000 attacks by spiders, mantises, birds, and other predators of spotted lanternflies. Also getting in on the act are naturally occurring soil fungi that have caused at least one lanternfly population to collapse in Pennsylvania. In addition, spotted lanternflies are reported to kill one of their favorite sources of food, invasive tree of heaven. Here’s hoping Mother Nature continues to send help in mitigating the invasion of spotted lanternflies.          

For more information on the biology and management of spotted lanternfly click here.

Acknowledgements

Thanks to James Murdock for providing inspiration for this episode. Thanks also to Eloise and Abby Kollins and Paula Shrewsbury for wrangling and spotting spotted lanternflies. Wonderful resources provided by scientists at Penn State University and Cornell University were consulted to prepare this episode. The fascinating article “A pair of native fungal pathogens drives decline of a new invasive herbivore” by Eric H. Clifton, Louela A. Castrillo, Andrii Gryganskyi, and Ann E. Hajek was used as a reference for this episode.

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From the Bug of the Week mailbag: What happens when a wheel bug goes for a spin? Wheel bug, Arilus cristatus

In previous episodes we met one of the toughest customers in Mother Nature’s gang of beneficial insects, the wheel bug. Wheel bugs play an important role reducing populations of noxious invasive pests like brown marmorated stink bugs and they also dine on important forest pests including fall webworms and other native caterpillars. This week we received the following message about a wheel bug that thought it might be fun to take a spin in a rotating core in a paper mill. Here’s the message. “I just thought you would be interested to know that this bug crawled inside of a core with a diameter of 4.41inches and this core went in our winder. He was rotated at 8000fpm for about 150 seconds start to finish and survived. Looks like he was a little dizzy but he ended up crawling out and then flying towards our control panel. So we determined he deserved to live so we caught him in a bag and took him outside. Crazy the endurance and survivability on this thing!!!” 

I am not exactly sure how far this predator spun around, but at 8000 feet per minute for 2.5 minutes seem like it might have traveled some 20,000 feet in circles. I don’t know about you, but I’d be dizzy, if I survived.

Wheel bugs are fierce generalist predators. Watch as this female stalks a dagger moth caterpillar. She slowly circles to the head of the caterpillar to deliver a lethal jab with her strong beak. After sizing up the prey with her left foreleg and extending her beak, she makes a lightning-fast strike to capture her prey. Forest pests like fall webworm caterpillars are also on the menu. This female snares a webworm while on a romantic interlude with her mate. Wheel bugs regularly dine on other pests including brown marmorated stink bugs. With other members of Mother Nature’s hit squad, they contribute to the decline of stink bugs in many parts of the country.  

To round out this episode, here is a little more about wheel bugs and how they roll when not in a paper mill. The wheel bug is a species of assassin bug and, as the name implies, it kills other insects. The common name, wheel bug, stems from the fact that this terror has a structure on its back that looks like a spoke-bearing medieval torture device. The function of this wheel is known only to Mother Nature and the bug, but not to me. The business end of the wheel bug is the powerful beak or proboscis stored between the beast’s front legs when it is not in use. Upon spying a tasty morsel, the wheel bug cautiously approaches, embraces the mark with long front legs, and impales the victim with the powerful beak. The wheel bug pumps strong digestive enzymes through the beak into the prey. These enzymes liquefy the body tissues of the hapless victim. A muscular pump in the head of the bug slurps the liquefied meal up through the beak. Young wheel bugs use protein from their prey for growth and development and adult females convert prey into eggs. In autumn, the well-fed female wheel bug lays barrel-shaped eggs in clusters of several to more than one hundred usually on the bark of a tree. Eggs hatch the following spring in May and June.  Small wheel bugs, called nymphs, are magnificent creatures with bright red abdomens and orange antennae. They dine on a wide variety of insects including caterpillars, sawfly larvae, beetles, and other bugs. In most years, I feel lucky if I witness a half dozen of these monsters at work in the wild. With plant nurseries and landscapes laden with invasive pests like stink bugs and spotted lanternflies, it is not unusual to see scores of wheel bugs stealthily stalking and assassinating their stinky marmorated cousins and other invaders. How much benefit results from greater numbers of these assassins remains to be seen, but we hope that these bugs and other naturally occurring predators and parasites will help stem the onslaught of brown marmorated stink bugs, spotted lanternflies, and other invasive species. If you encounter wheel bugs, please heed this caution. While holding and admiring a wheel bug, I learned firsthand, so to speak, that the wheel bug could deliver a memorable, painful poke with its beak. If you keep wheel bugs as pets beware, try not to handle them directly or you too may become an unwitting victim of this clever assassin.

Acknowledgement

We thank Joshua Colgin for providing images and the fascinating story that inspired this episode.

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From the Bug of the Week mailbag: What happens when a wheel bug goes for a spin? Wheel bug, Arilus cristatus

In previous episodes we met one of the toughest customers in Mother Nature’s gang of beneficial insects, the wheel bug. Wheel bugs play an important role reducing populations of noxious invasive pests like brown marmorated stink bugs and they also dine on important forest pests including fall webworms and other native caterpillars. This week we received the following message about a wheel bug that thought it might be fun to take a spin in a rotating core in a paper mill. Here’s the message. “I just thought you would be interested to know that this bug crawled inside of a core with a diameter of 4.41inches and this core went in our winder. He was rotated at 8000fpm for about 150 seconds start to finish and survived. Looks like he was a little dizzy but he ended up crawling out and then flying towards our control panel. So we determined he deserved to live so we caught him in a bag and took him outside. Crazy the endurance and survivability on this thing!!!” 

I am not exactly sure how far this predator spun around, but at 8000 feet per minute for 2.5 minutes seem like it might have traveled some 20,000 feet in circles. I don’t know about you, but I’d be dizzy, if I survived.

Wheel bugs are fierce generalist predators. Watch as this female stalks a dagger moth caterpillar. She slowly circles to the head of the caterpillar to deliver a lethal jab with her strong beak. After sizing up the prey with her left foreleg and extending her beak, she makes a lightning-fast strike to capture her prey. Forest pests like fall webworm caterpillars are also on the menu. This female snares a webworm while on a romantic interlude with her mate. Wheel bugs regularly dine on other pests including brown marmorated stink bugs. With other members of Mother Nature’s hit squad, they contribute to the decline of stink bugs in many parts of the country.  

To round out this episode, here is a little more about wheel bugs and how they roll when not in a paper mill. The wheel bug is a species of assassin bug and, as the name implies, it kills other insects. The common name, wheel bug, stems from the fact that this terror has a structure on its back that looks like a spoke-bearing medieval torture device. The function of this wheel is known only to Mother Nature and the bug, but not to me. The business end of the wheel bug is the powerful beak or proboscis stored between the beast’s front legs when it is not in use. Upon spying a tasty morsel, the wheel bug cautiously approaches, embraces the mark with long front legs, and impales the victim with the powerful beak. The wheel bug pumps strong digestive enzymes through the beak into the prey. These enzymes liquefy the body tissues of the hapless victim. A muscular pump in the head of the bug slurps the liquefied meal up through the beak. Young wheel bugs use protein from their prey for growth and development and adult females convert prey into eggs. In autumn, the well-fed female wheel bug lays barrel-shaped eggs in clusters of several to more than one hundred usually on the bark of a tree. Eggs hatch the following spring in May and June.  Small wheel bugs, called nymphs, are magnificent creatures with bright red abdomens and orange antennae. They dine on a wide variety of insects including caterpillars, sawfly larvae, beetles, and other bugs. In most years, I feel lucky if I witness a half dozen of these monsters at work in the wild. With plant nurseries and landscapes laden with invasive pests like stink bugs and spotted lanternflies, it is not unusual to see scores of wheel bugs stealthily stalking and assassinating their stinky marmorated cousins and other invaders. How much benefit results from greater numbers of these assassins remains to be seen, but we hope that these bugs and other naturally occurring predators and parasites will help stem the onslaught of brown marmorated stink bugs, spotted lanternflies, and other invasive species. If you encounter wheel bugs, please heed this caution. While holding and admiring a wheel bug, I learned firsthand, so to speak, that the wheel bug could deliver a memorable, painful poke with its beak. If you keep wheel bugs as pets beware, try not to handle them directly or you too may become an unwitting victim of this clever assassin.

Acknowledgement

We thank Joshua Colgin for providing images and the fascinating story that inspired this episode.

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In previous episodes we visited delightful mason bees as they made an early debut and foraged for nectar and pollen to provision their nests inside cardboard tubes and galleried firewood in a mason bee colony. Tiny bee larvae will spend the next several months completing development before pupating in their chambers come fall, but right now all is not well in the realm of mason bees. Enemies are afoot. For the past several weeks, gangs of noisy yellow and black insects, leucospid wasps, have been carefully inspecting the modular condominiums of my mason bee colony. Leucospids are generally considered rare insects, but each year the tubular homes and woody tunnels housing mason bees attract scads of these parasites.

My mason bee condominium of cardboard tubes and galleries in wood provides homes for hundreds of mason bees to raise their young. But as spring turns to summer, danger arrives. Bee babies are hunted by clever leucospid wasps. With antennae tapping, a female leucospid wasp searches a mason bee log for clues to locate potential victims within. Once the bee larvae are located, she unsheathes the ovipositor and drills into the log to lay her eggs. In slow motion, watch as she unfolds her ovipositor and pirouettes on tip toes to drill into the wood. After depositing her eggs in the brood chamber, she pulls her ovipositor out and prepares to locate the next victim.  

Leucospids are rather unique in the wasp world. Unlike most of their kin with rear-facing or under-slung egg-laying tubes called ovipositors, leucospids carry their ovipositor arched up and over their back. The small yellow and black wasps move back and forth across the surface of the mason bee’s tubes and wooden lodgings tapping gently with their antennae and drumming with their abdomen. This behavior has been noted in other species of leucospids and is likely how the female wasp evaluates where the bee larvae reside and, perhaps, the suitability of the mason bees as a meal for her young. If the female leucospid likes what she finds, she uses her remarkable ovipositor to penetrate the cardboard tubes or my tough oak logs. She deposits eggs inside the cells of the developing mason bees. It is fascinating to watch the female wasps insert her ovipositor into mason bee galleries in search of bee larvae to serve as food for her young. After a few days, the wasp’s eggs hatch into voracious larvae that feed as ectoparasites attached to the outside of the bee larvae. Larvae of the parasitic wasps complete development and emerge as adults to find a mate and search for more victims.

I pondered the peril of my mason bee colony and soon realized that many of my hard-working bees would be spared from the treacherous leucospid wasp. When it comes to attacking bee larvae hidden in tubes, size does matter. The ovipositor of the leucospid wasp is only long enough to penetrate the outermost tubes of my modular mason bee condominium. Likewise, holes drilled in the center of my mason bee logs will remain unscathed. The vast majority of mason bees sheltered therein are well beyond the reach of leucospid’s dangerous egg-laying appendage. While some mason bee aficionados might cover their bee condominiums with netting to prevent parasitism, I let nature take its course. Rare leucospids are magnificent in their own way and part of the circle of life in the realm of insects.  

References

Two interesting articles, “Parasitic Behavior of Leucospis cayennensis Westwood (Hymenoptera: Leucospidae) and Rates of Parasitism in Populations of Centris (Heterocentris) analis (Fabricius) (Hymenoptera: Apidae: Centridini)” by Ana Lúcia Gazola and Carlos Alberto Garófalo, and “Osmia ribifloris, a Native Bee Species Developed as a Commercially Managed Pollinator of Highbush Blueberry (Hymenoptera:Megachilidae)” by P. F. Torchio, were used as references for this episode.

 

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How can you not love Greek mythology? Polyphemus, a terrible, one-eyed giant that enjoyed feasting on men, notably Odysseus and his crew. Fitting that to escape from the cave of Polyphemus, the crew blinded him with a spear and snuck out of the cave with a herd of sheep. Giants also populate the world of insects. Polyphemus is the name given to one of our largest moths that has not one eye, but four on its dorsal wings. These are not true eyes like the compound eyes on the head of the Polyphemus moth. These false eyes or eyespots are an evolutionary masterpiece created by hundreds of colored scales arranged in patterns resembling the eye of another animal like a bird, mammal, or snake.

This montage begins with a very pregnant female Polyphemus moth that decided to lay her eggs on a lawn chair. Hopefully, the caterpillars made their way to an oak or maple tree like this one. Here is what this giant silk moth caterpillar looks like as it ascends the tree. Watch as smaller and larger caterpillars munch on one of their favorite foods, the leaves of oaks. One kind human found this female Polyphemus marooned inside a parking garage after a storm. With a little assistance, this magnificent moth took flight. Here’s looking at you Polyphemus.  Video and image credit: Nancy Koran, Peihan Orestes, and Jenny Milward.

Several species of insects employ clever patterns of coloration resembling eyes on parts of their body where eyes really do not occur. For example, in a previous episode of Bug of the Week, we met the larva of the swallowtail butterfly adorned with two sinister eyespots on its thorax. These false eyes helped create the illusion of a serpent for a larva that is really a tasty caterpillar. Scientists believe that these eyespots aid in defense of insects and other animals in several ways. Eyespots may resemble the eyes of a potential predator’s own predators. Moths and butterflies are tasty fare for many birds, but in turn, birds are meals for larger winged predators such as owls. Eyespots and color patterns on the wings of some moths resemble the face of an owl. Imagine the terror of a bird about to eat what appears to be a harmless moth, when suddenly the hungry bird confronts the face of an owl. A second way that eyespots may aid in defense is to direct an attack away from vulnerable parts of the body. Some predators attack the head of the victim where maximum damage results. False eyespots on less critical parts of the body such as wings may steer a first strike away from a lethal spot and provide time for the intended prey to escape.

Last week, I received images of a very pregnant female Polyphemus moth that had settled on a patio and proceeded to lay batches of eggs on a lawn chair. I know not what became of the eggs or the moth, but with luck the eggs hatched and the tiny caterpillars, which don’t eat lawn chairs, found their way to sustaining leaves of elm, oak, walnut, or more than a dozen other woody trees and shrubs. These marvelous caterpillars will gain more than a thousand times their birth weight before they spin cocoons of leaves and silk and change into pupae. With luck, in a few weeks, we will have dozens of four-eyed moths returning to the wild to scare the daylight out of would-be predators.     

Acknowledgement Special thanks to Nancy Koran for providing inspiration and images for this episode. Cool camera work by Peihan Orestes and Jenny Milward helped create this story. The fantastic Caterpillars of Eastern North America by David Wagner was used as a reference.      

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Last week we met voracious flower fly larvae as they ravaged populations of brown ambrosia aphids on my silphium cup plant. This week things have gone from bad to worse for the pesky aphids as populations of sneaky predatory aphid midges arrived in force and rained carnage on the aphids. In past episodes, we visited many wild predators like firefly larvae, tiger beetles, and spiders that employed powerful jaws or fangs to slice, dice, and consume hapless prey. Today we meet a predaceous midge, Aphidoletes aphidomyza, with a fondness for the legs of aphids. Hold on, a fondness for legs, what’s that about? Here’s the story. Larvae of predaceous midges are many times smaller than those of the large flower flies we met last week. In fact, they are much tinier than the aphids on which they feast. These diminutive predators sneak up on the victims and with persistence and luck, they attach themselves to the joints on the aphid’s leg. After they are plugged in, they inject paralytic venom, likely produced in their salivary glands, into the blood stream of the aphid. In a matter of minutes, the paralytic action of the venom takes hold immobilizing the aphid. As I watched one of these attacks, I saw a small midge larvae intermittently strike and bite  the left foreleg of a small aphid. As the movements of the aphid subsided, the midge slowly slithered beneath the aphid and attached itself to the right hind leg of the moribund aphid. Half an hour later the midge moved to the left hind leg. With its victim motionless, the predator finally settled on rump of aphid for its meal. After subduing their victims, midge larvae may move to meatier parts of the aphid’s body such as the thorax where they may be joined by other larvae.  Some accounts report that these tiny assassins will kill more aphids than they consume. Not sure how to explain that. The aftermath of the midge’s carnage is blackened hulks of shrunken exsanguinated aphids. 

Aphids dance away from a predaceous midge larva searching for a victim. This one snared the left foreleg of a small aphid and is injecting paralytic venom. Next it moves to the right hind leg of the moribund aphid. Then on to the left hind leg. With the aphid motionless, the larvae settles on ‘rump of aphid’ for dinner. Nearby, two midge larvae feed on the head of an aphid. When these tiny monsters are done, all that remains of the aphid colony are shriveled black carcasses.

These brown ambrosia aphids are not entirely defenseless. Watch as one drop kicks a predatory midge right off a leaf. Here’s the instant replay at one tenth normal speed.

In the killing field of Aphidoletes aphidomyza after the feast, all that remains are black shriveled carcasses of aphids. Photo by Mike Raupp

If you are feeling a bit sorry for the poor aphids in all of this, I understand. Their demise seems gruesome, meeting death by mouth hooks and venom producing flies. But remember that aphids are major pests of our crops and landscape plants causing billions of dollars of loss worldwide. Predaceous midges are key players in mitigating losses to pests in natural and managed ecosystems. They are produced commercially and regularly used in greenhouses as biological control agents for aphids.  To learn more about   Aphidoletes as biological control agents, please click on the links below.

https://biocontrol.entomology.cornell.edu/predators/Aphidoletes.php

https://ipm.ucanr.edu/natural-enemies/aphid-midge/#gsc.tab=0

Acknowledgements: Bug of the Week thanks Dr. Shrewsbury for spotting predaceous midges in the aphid outbreak on the cup plant. The informative articles “Entomo-venomics: The evolution, biology and biochemistry of insect venoms” by Andrew Walker, Samuel D. Robinson, David K. Yeates, Jiayi Jin, Kate Baumann, James Dobson, Bryan G. Fry and Glenn F. King and “Aphid Predatory Midge” by Jim Walgenbach were used as references for this episode.

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