EPA Approves Zika-Fighting Genetically Modified Mosquitoes

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In a previous episode we lamented the unusual paucity of large swallowtail butterflies in our gardens this year. But 2020 has not been a rotten season for all of our six and eight legged friends. Over the past few weeks, I have received several images and a few videos of black and yellow garden spiders who have made their homes in flower beds and gardens here in the DMV. Some of us have shared the experience of wandering along a path through a meadow and bumbling into an enormous spider web ruled by a fearsome yellow and black spider.

Argiope aurantia, the so-called black and yellow garden spider, is extraordinarily common this year in some locations. Webs of the black and yellow garden spider can be gargantuan, often spanning several feet. Fortunately for Bug of the Week and for the first time in several years, one of these gorgeous arachnids, a female by the name of Sylvia, has taken up residence amongst my zinnias where she helps to keep blow flies, stink bugs, and other less desirable arthropods at bay.

One of our past resident black and yellow garden spiders, Charlotte, demonstrates her skill at immobilizing and capturing prey. A brown marmorated stink bug stands no chance once it encounters the sticky strands of the web. Charlotte’s attack is eerily reminiscent of Frodo’s unfortunate encounter with Shelob in route to Mount Doom. After immobilizing the stink bug, she returns to feast on the remains of a former, now unrecognizable, victim. Spiders, along with many other home-grown predators, are part of the reason stink bugs are not the problem they once were here in the DMV.

One of the signature features of Sylvia’s web and those of other orb weavers is the construction of a zigzagging band of dense silk called a stabilimentum near the center of her web. The function of the stabilimentum is a topic of debate among arachnologists. Some suggest that the band helps disguise the spider from its predators by providing a form of camouflage as the spider rests in the center of its web. Others believe that the silk may act as a tiny parasol shielding the spider from intense rays of the sun. One fascinating study revealed that the conspicuous bands of silk acted as a visual warning to low flying birds, reducing the likelihood of devastating web-destroying crashes much the same way an image of an owl on a large plate glass window dissuades misguided birds from crashing and breaking their necks. Of course, the spider cares not for the welfare of the bird, but repairing bird-damaged webs takes time away from important projects like capturing and eating insects.

One recent misty morning, more of a rule than an exception this year, provided a grand opportunity to witness another curious behavior of Sylvia the orb weaver, her skill at web-flexing. While stationed near her stabilimentum and grasping strands of silk, Sylvia flexed and extended her front legs repeatedly. Her rhythmic gyrations set the entire web rocking back and forth. Swaying the web in rhythmic motion is called web-flexing, a behavior often observed in orb weavers. Web-flexing has been reported as a way to dislodge potential predators, or to cause prey to become entangled in sticky capture-threads in the web. Flexing may serve other defensive purposes as well. Enemies of the orb weaver include predatory lizards, toads, and other spiders that rely on keen eyesight to locate and capture prey. In an interesting treatise on orb weavers, Wayne Tolbert suggested that web-flexing might be a clever way for the spider to conceal its exact location, thereby confounding hungry predators. On this rainy morning I wondered if Sylvia’s vigorous web-flexing might be a way to shed raindrops from the silken capture-threads of her orb. When you see orb weavers and other spiders in your gardens and landscapes, please avoid any urge to destroy them. We have found spiders to be one of the most important group of predators putting a beat-down on common pests of ornamental plants in residential landscapes.

On a rainy morning, Sylvia, a black and yellow garden spider, uses her forelegs to rock her web back and forth. This behavior known as web-flexing may help her snare prey, dodge predators, or, perhaps, shed raindrops that accumulate on capture-threads of her web. Another black and yellow garden spider has had a very successful season producing two marble-sized egg cases from her harvest of prey. Video credits: Michael Raupp and Ann Payne

Acknowledgements

Bug of the Week thanks Anne Payne, Jill Moore, Steve Hand and Gene Ferrick for sending images and videos and for donating black and yellow garden spiders, inspiriting this episode. Three great articles, “Predator avoidance behaviors and web defense structures in the orb weavers Argiope aurantia and Argiope trifasciata” by W. Tolbert, “Do stabilimenta in orb webs attract prey or defend spiders?” by T.A. Blackledge and J.W. Wenzel, and “Do top-down or bottom-up forces determine Stephanitis pyrioides abundance in urban landscapes?” by Paula Shrewsbury and M.J. Raupp, were consulted for this episode.

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Last week while driving from Maryland to New Jersey along Route 30 in southeastern Pennsylvania, I stopped for a bite to eat in scenic Rohrerstown. This once forested town settled by the Pennsylvania Dutch now finds itself the home of a new six-legged settler from Asia, the spotted lanternfly. We met the spotted lanternfly in previous episodes of Bug of the Week where we learned about its discovery in Berks County in 2014, how it moved to locations nearby, and what citizens could do help local officials track its movement and slow the spread of this killer of vineyards.

Lanternfly adults and their youngsters, called nymphs, remove large quantities of phloem sap from woody plants as they feed. The excess is excreted from their rear end in copious amounts as a sugary waste product called honeydew. More than 103 plant taxa of woody and herbaceous plants serve as hosts for spotted lanternflies. Spotted lanternflies can be severe pests of fruit and shade trees, grapes, and hops. Massive infestations in vineyards have withstood repeated applications of insecticides and still caused the demise of entire vineyards. In home landscapes, hundreds of these rascals have been observed feeding on a single plant, where they rain scads of honeydew onto vegetation and the earth below. As with honeydew produced by other phloem feeders such as soft scales and aphids, the honeydew excreted by lanternflies fouls foliage, fruit, and underlying plants, and serves as a substrate for the growth of a fungus known as sooty mold. Honeydew makes leaves sticky and fruit unmarketable, and sooty mold further disfigures leaves and fruit and may impair photosynthesis. This presents a huge economic problem for growers of apples, cherries, peaches, and grapes. Sweet honeydew and its fermentation products also attract a variety of stinging insects like yellow jackets and paper wasps. In addition to excreting honeydew, lanternflies may be so numerous that they cause wilting and dieback of branches.   

While I munched a panini at an outdoor table, I was astonished to see airborne spotted lanternflies crashing into plate glass windows of nearby buildings. The nearest trees that might have spawned these aeronauts were several hundred yards away. Earthbound lanternflies dashed across sidewalks and streets and hapless lanternflies met untimely death beneath the feet of pedestrians and wheels of cars. Amidst a concrete jungle, I wondered where these buggers had come from and how they got there. One somewhat harebrained possibility was that they hiked as nymphs from egg masses laid on stones or Ailanthus trees bordering a distant hedgerow and spent their youth sucking sap on one of a dozen red maples struggling to survive in small concrete coffins in the center of the parking lot. A clever study conducted by Kelli Hoover and her colleagues at Penn State found that some spotted lanternfly nymphs travel as much as 213 feet in their quest to find a suitable host, but only about half would travel 56 feet. While this pretty much ruled out a hike from the hedgerow, a quick check of the maple trees confirmed no signs of occupation by lanternflies and infirmed my nymphs-take-a-hike hypothesis. More likely, of course, is that these travelers developed on distant trees and were on their way somewhere else.

On a sunny late summer afternoon in a restaurant park in scenic Rohrerstown, PA, spotted lanternflies were on the wing. They crashed into windows, wandered on sidewalks, and met gruesome ends beneath human feet and tires of vehicles. Wanderers displayed their impressive jumping skills when harassed by a giant finger and one contemplated a trip to New Jersey on the rear bumper of my car.

In addition to being capable flyers, I learned that they were excellent jumpers as well, much to the amusement of fellow diners watching my feeble attempts to capture the earthbound insects. When I finally snagged a couple I found them to be rather trim, unlike rotund lanternflies I had discovered on the trunks of trees in the latter weeks of autumn in previous years. Recent studies by scientists in Pennsylvania reveal some of the secrets to the autumnal movements of adult spotted lanternflies. Thomas Baker and his colleagues at Penn State discovered that these slim fancy flyers are primarily unmated females capable of flights ranging from roughly 30 to 150 feet. Their spontaneous flights are believed to be quests to find suitable hosts, plants that will supply sufficient nutrients for them to fatten up and deposit a complete complement of eggs before cold weather puts an end to their mischief. The Penn State team also assessed the flight worthiness of plump yellow-bellied lanternflies. A vast majority of these heavy females had successfully mated but their ability to fly was weak and limited to only about 12 feet when launched into the air.

While autumnal spontaneous flights have been witnessed on a regular basis, these relatively short distance flights of hundreds of feet likely account for only a minor component of the spotted lanternflies’ spread to adjacent counties and states. From their initial discovery point in Berks County in 2014, isolated spotted lanternflies have been recovered in eastern Massachusetts some 270 miles distant and in Buncombe County, North Carolina almost 500 miles away. According to entomologist Julie Urban, also at Penn State, the most likely explanation for these long distance peregrinations lies in human-assisted transport of lanternfly eggs. It is believed that spotted lanternflies arrived in Pennsylvania around 2012 from Asia in a shipment of stone products bearing lanternfly eggs, a trip of some 7,000 miles. Unlike many herbivorous insects that lay eggs on food plants for their young, spotted lanternfly mothers deposit egg masses on non-host objects including stones, cinder blocks, lawn furniture, and vehicles, in addition to trees. These nondescript masses of eggs are easily overlooked on natural and human-made items and easily transported inadvertently by road or rail. Unfortunately, at the epicenter of the spotted lanternfly infestation in southeastern Pennsylvania, Delaware, and New Jersey, several major interstate highways and railways run north and south, east and west, crisscrossing a region replete with warehouses, truck stops, and railroad depots embedded in a matrix of orchards, vineyards, and forests that serve as hosts for lanternflies.  

This map shows the current locations of established infestations of spotted lanternflies (blue counties), internal state quarantines are outlined in red, and counties with isolated detections have a small purple dot. Map courtesy of Brian Eshenaur and the New York State Integrated Pest Management Program of Cornell University.

So, how far will spotted lanternfly spread in the US? Based on recent climatic data from the US and Asia, scientists suggest that much of the mid-Atlantic and Central regions of the US and portions of California, Oregon, and Washington State have climates suitable for the survival of spotted lanternfly. In addition to well-established infestations in Pennsylvania, Virginia, Delaware, New Jersey, West Virginia, and Maryland, isolated living or dead individuals have been found in more than three dozen locations in the previously listed states and also in New York, Connecticut, and Massachusetts. As I finished my lunch and headed back to my car, I noticed a skinny spotted lanternfly perched on my rear bumper ready to hit the road with me to the Garden State. As I constructed this tale last week, I received an update that several living spotted lanternfly adults had been spotted in Greenwich, Connecticut. So, if you travel in the aforementioned infested zones in autumn, when you stop for a biobreak, meal, or fuel, please give yourself and your vehicle a quick once over to be sure you are not transporting these clever hitchhikers.  Will spotted lanternflies soon be coming to your neighborhood? Time will tell, but as I have often heard said, you can usually bet on the bug. (BTW, of course I removed the lanternfly from the bumper of my car and inspected it for other hitchhikers before I drove away.)

This map shows the potential distribution of spotted lanternfly in the United States based on climatological data. Areas with the highest probability of supporting lanternflies appear in dark orange and areas unsuitable for lanternflies are white. Map courtesy of the Entomological Society of America at Entomology Today, October 3, 2019. 

To learn more about spotted lanternfly please visit the brilliant, fact-packed Penn State Cooperative Extension Website at this link: https://extension.psu.edu/spotted-lanternfly 

To watch a video of spotted lanternflies in flight, please click this link.

Acknowledgements

Bug of the Week thanks Dr. Shrewsbury for spotting and wrangling spotted lanternflies for this episode. We acknowledge the great work of scientists contributing to our knowledge of this pest, with particular thanks to authors of articles used as references including “Worldwide Feeding Host Plants of Spotted Lanternfly, With Significant Additions from North America” by Lawrence Barringer and Claire M. Ciafré, “Perspective: shedding light on spotted on lanternfly impacts in the USA” by Julie M. Urban, “Dispersal of Lycorma delicatula (Hemiptera: Fulgoridae) Nymphs Through Contiguous, Deciduous Forest” by Joseph A. Keller, Anne E. Johnson, Osariyekemwen Uyi, Sarah Wurzbacher, David Long, and Kelli Hoover, and “The Establishment Risk of Lycorma delicatula (Hemiptera: Fulgoridae) in the United States and Globally” by Tewodros T. Wakie, Lisa G. Neven, Wee L. Yee, and  Zhaozhi Lu. Thanks to Brian Eshenaur and the entire team at the New York State Integrated Pest Management Program of Cornell University for providing the updated maps of spotted lanternfly in the US and to the Entomological Society of America for providing the map of the potential distribution of spotted lanternfly in the US.

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Last week a keen naturalist shared images and videos of a rather large caterpillar taking a stroll along what appeared to be a paved path or roadway. While rather homely in its youth, this giant larva turns into one of the most astoundingly beautiful moths found on the planet, the Imperial moth. In previous episodes we met other gorgeous members of the giant silk moth clan including, Promethea, Polyphemus, Royal Walnut, Luna, and Cecropia. As the name implies, silk moths produce silk from spinnerets associated with their mouthparts. Several species use this silk to form a durable cocoon in which to pupate and survive winter’s chill. However, larvae of the Imperial moth burrow into the ground and form an earthen chamber in which they transform to a pupa. With the return of warm weather, adult Imperial moths emerge from the soil to seek mates. At night, females fly to the canopy of trees where they release sex pheromones to attract a suitor. Following a successful romantic interlude, females deposit eggs singly or in groups of 2 to 5 on leaves. Caterpillars hatch from the eggs in about two weeks and then feed for several more on the leaves of a wide variety of woody and evergreen trees. Dr. Douglas Ferguson, an expert on silk moths, lists oak, hickory, walnut, sycamore, basswood, maple, honey locust, chokecherry, sumac, sweet gum, sassafras, elm, beech, hornbeam, birch, alder, pine, spruce, hemlock, cedar, cypress, and juniper as food sources of Imperial moth caterpillars. The prodigious appetites of Imperial moth caterpillars ensure that larvae acquire adequate nutrients to sustain them both during larval development and also as adults. Mouthparts of Imperial moths are vestigial; adults do not feed.  

In late summer and early autumn, Imperial moth caterpillars depart their lofty feeding grounds in the canopies of trees. After a perilous journey across human-made structures like pathways and roads, they reach the safety of soil where they will disappear underground to form pupal chambers. With the return of warm weather and foliage on trees, beautiful adult moths will emerge from the earth to mate and deposit eggs on leaves.

Imperial moths are found from Canada to Argentina, although populations of Imperial moths in parts of New England have declined. This is very evident in states such as Connecticut, where experts report the Imperial moth to be extirpated. Some believe this decline is linked to insecticide applications used in agriculture or to control nefarious gypsy moth caterpillars. Release of exotic parasitoid flies that attack and kill not only gypsy moth caterpillars but also other caterpillars, including several members of the silk moth clan, may also contribute to the demise of Imperials. Another factor believed to imperil Imperial moths and their relatives are high intensity street lamps that are very attractive to night-flying moths. These artificial illuminators may expose insects to predators or disrupt the normal mating rituals of many insects, including silk moths. Despite the decline of Imperial moth in parts of New England, this remarkable insect thrives throughout much of its range in North, Central, and South America.  The image of the adult Imperial moth in this episode was taken on a maple tree at a child care center in Columbia, Maryland. Although rare or absent in much of New England, on the isle of Martha’s Vineyard a sturdy, pine-eating race of Imperial moths seems to have escaped the perils of habitat destruction, pesticides, and imported parasitoids. For fortunate vacationers heading to that picturesque island, the Imperial moth serves as a spectacular reminder of a less human-muddled natural world.

Acknowledgements

Bug of the Week thanks Frank Roylance for sharing video and images that inspired this episode, Dr. Shrewsbury for spotting an Imperial moth caterpillar dawdling on a tree trunk along the C & O canal, and Harry Walker of Child’s Garden for alerting us to the beautiful Imperial moth on a maple tree at his day care center. “Life history of the Imperial Moth Eacles imperialis (Drury) (Saturniidae: Ceratocampinae) in New England, U.S.A.: distribution, decline, and nutritional ecology of a relictual islandic population” by Paul Goldstein, “The moths of America North of Mexico, Fascicle 20.2A Bombycoidea: Saturniidae (Part)” by Douglas C. Ferguson, “Moth decline in the Northeastern United States” by David L. Wagner, and “Common name: imperial moth, scientific name: Eacles imperialis imperialis (Drury, 1773) (Insecta: Lepidoptera: Saturniidae: Ceratocampinae)” by Donald Hall provided excellent background information for this episode.

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Several years ago while at work pulling weeds in a bed of chrysanthemums, I noticed a liberal sprinkling of caterpillar frass decorating blossoms of several plants. Frass, the euphemistic term for the pellet-like, powdery, or sawdust-like excrement of herbivorous insects, often provides a clue alerting one to the presence of an insect on or in a plant. A thorough inspection of my mums failed to disclose the culprit, but as I watched the plant later while enjoying a leisurely cup of coffee, I noticed a small cluster of flowery debris swaying on a blossom. A closer inspection revealed a cleverly disguised caterpillar cloaked in purple petals busily dining on the flower head. Recently, several eagle-eyed naturalists have reported similar sightings on mints and Joe Pye weeds in gardens and meadows. While I have yet to discover them in my garden this season, if the rain ever abates, I will renew my search with vigor.

This little trickster is the camouflaged looper, Synchlora aerate. Bedecked with bits of foliage and flower petals, it is sometimes detected when performing a herky-jerky waltz as it moves from one meal to the next. We’ve all seen the movie where a warrior incorporates leaves and branches into a camouflaged uniform to hide from the enemy, right? Next time you see this in a flick, just remember that a caterpillar thought of it first several million years ago. If you have a moment to sit and watch a stellar performance you may see the looper sway back and forth, adding to the illusion of a plant part being blown by the wind.

Imagine you are a camouflaged looper. When dining on coreopsis, browns and yellows seem the smart camo choice. But when crimson mums are on the menu, better go with the crimson petals. And when you depart for the next meal add a little “I’m just a petal swaying in the breeze” movement to your routine to fool the eyes of hungry predators.

Loopers are members of a large family of moths known as geometrids. The name geometrid stems from Greek roots meaning “earth measure”. Another common name for some geometrid caterpillars is inchworms. As they cruise about the blossoms, loopers and inchworms do appear to measure the earth inch by inch. In addition to my chrysanthemums, camouflaged loopers eat many other types of flowers including ageratum, aster, black-eyed Susan, boneset, coreopsis, daisy, goldenrod, Joe Pye weed, ragweed, raspberry, rose, sage, St. John’s wort, and yarrow. The adult stage of the camouflaged looper is known as the wavy-lined emerald and it is every bit as beautiful as the larva. So next time you see some unexpected frass on your flower blossoms, take a few moments to observe your flowers with an eye out for these masters of disguise.

Can you spot the camouflaged looper on this mint? Well, for the one eating goldenrod some labels and an arrow might help. Photo credits: mint – Mara McCall, goldenrod – Mike Raupp.

Acknowledgements

Many thanks to our observant naturalists who discovered camouflaged loopers in their landscape, especially Mara McCall and Glen Schulze for providing the inspiration for this episode and for providing cool images of these rascals. The wonderful reference “Caterpillars of Eastern North America” by David Wagner was used as a reference for this Bug of the Week.

BTW, in the feature image the head is on the left and the rear end is on the right.

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Although this year has been tough on some charismatic butterflies, it seems to have been a great year for wasps. Earlier this year giant murder hornets made a sensational splash when they were discovered in the Pacific Northwest. And here in the DMV we have visited cow killers hunting bumble bees, great black wasps capturing katydids, cicada killers living up to their name, and tiny Aphidius wasps exiting the rear end of aphids. This week, let’s visit a pair of gorgeous and really cool wasps intent on annihilating   dastardly beetle pests in our lawns and gardens.

The beetle pests these wasps focus on include larval stages (a.k.a. grubs) of green June beetles, Japanese beetles, Oriental beetles, Asiatic garden beetles, and other members of the scarab clan that dwell in soil and devour roots of our lawn grasses in addition to those of annual and perennial plants. As adults these beetles, known as scarabs, strip leaves and blossoms of hundreds of species of ornamental plants and wholesome vegetables. Abundant spring and summer rains conducive to grub survival have turned my flower beds into ideal breeding sites for these rascals. But in Mother Nature’s system of checks and balances, it is not unusual to see populations of predators and parasites rise shortly after populations of their prey increase. Over the past week or so, several folks have commented on hordes of dark winged wasps cruising back and forth a foot or so over their turf. Most of these sightings are digger wasps, members of a family known as Scoliidae. The digger wasp moniker stems from the impressive ability of these fierce fliers to locate white grubs beneath the surface of the earth, tunnel through the dirt, deliver a paralyzing sting, and deposit an egg on the skin of the grub. The hapless white grub is incapable of removing the egg, which soon hatches and the parasitic larva of the digger wasp slowly consumes its living victim. Glad I’m not a white grub.  After completing its development during summer and autumn, the wasp larva spins a silken cocoon, pupates, and then passes the winter in the burrow created by the grub. Fresh, new wasps emerge as adults the following August.

Whether it’s small white grubs in the soil or zany green June beetle grubs that crawl on their back across the ground, these pests face an awesome grim reaper when Scolia wasps come to my garden. Video credit: Michael J. Raupp

Several species of digger wasps can be found in the DMV and two in the limelight this time of year are Scolia dubia and Scolia nobilitata. Commonly known as the blue-winged digger wasp, Scolia dubia sports striking iridescent blue-black wings. Its body is black excepting the end of its fuzzy abdomen, which is reddish brown. Scolia dubia is easily recognized by one pair of bright yellow spots on either side of its abdomen. Its cousin, Scolia nobilitata, has smoky brown wings with two pair of yellow or off-white spots on its abdomen. These colorful beauties need energy to search for grubs and tunnel underground to find their victims. They can often be seen carbo-loading in preparation for the hunt on nectar-rich members of the mint family (Lamiaceae) such as mountain mint and spotted horse mint, and members of the aster family (Asteraceae) such as goldenrod. Lawns and landscape beds rampant with white grubs often attract squadrons of digger wasps flying in tight figure-eight patterns just above the ground, presumably hunting for prey. While they might appear scary, please understand that these wasps are not aggressive towards humans and that they are highly beneficial by virtue of the beat-down they put on white grubs. You can befriend these beneficial wasps by providing nectar sources, mints and asters, in your landscape and thereby invite them to hang around and find some pestiferous white grubs to serve as food for their offspring. As part of Mother Nature’s system of checks and balances, plant some flowers, sit back and relax on a warm autumn day and let them do their work.

Mints and goldenrods bring digger wasps like Scolia dubia to your garden on sunny days in late summer and autumn. After tanking up on energy-rich nectar, they will search for white grubs in your lawn and gardens, dig into the soil, and deposit eggs on hapless grubs. Upon hatching, wasp larvae devour the grubs and thereby help to rid your landscape of these noxious pests. Video credit: Marie Rojas and Michael J. Raupp

Acknowledgements

Bug of the Week thanks Marie Rojas for the awesome video of blue-winged digger wasps nectaring on mountain mint and Dr. Shrewsbury for providing the inspiration for this episode. The wonderful books “Destructive Turfgrass Insects” by Dan Potter and “Bees, Wasps, and Ants” by Eric Grissell were used as references.

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During a recent conversation with a Master Naturalist over some holes in leaves of ornamental mallows, I shared my inability to find one of the usual suspects associated with shredded mallow leaves, the mallow sawfly, a wasp we met in a previous episode. My rather public response elicited a flurry of rejoinders from gardeners and naturalists whose dogwoods were ravaged this year by another member of the sawfly clan, called the dogwood sawfly. Sawflies are primitive members of the bee and wasp order of insects known as the Hymenoptera. Unlike their kin, who either feast on the flesh of other arthropods or dine on nectar and pollen of plants, several families of sawflies feed on leaves. So this week seems to be a good time to catch up with a couple of fascinating leaf-munching sawflies.

Let’s start with dogwood sawfly. One of the favored hosts of dogwood sawfly is grey dogwood, Cornus resemosa, but silky dogwood, Cornus amomum, and flowering dogwood, Cornus florida, are also on the menu. Winter is spent as a larva ensconced in a chamber built in rotting wood or sometimes structural wood, including siding. In spring larvae pupate and later, from May through July, adults will emerge to fly and find mates. Females deposit eggs on the undersurface of dogwood leaves in clutches numbering 100 or more. Eggs hatch and larvae consume leaf tissue and develop through summer. With the approach of autumn and imminent leaf drop, large sawfly larvae wander from dogwood trees to construct overwintering redoubts in wood. Although many sawfly larvae bear a striking resemblance to caterpillars, the larvae of moths and butterflies, most can be distinguished from Lepidoptera larvae by the number of pairs of appendages called prolegs found on abdominal body segments. In addition to three pairs of jointed walking legs on the thorax, most caterpillars have five or fewer pairs of fleshy prolegs on their abdominal segments. By contrast, in addition to the requisite three pairs of thoracic legs, most sawflies bear six or more pairs of prolegs.

Snaky dogwood sawfly larvae practice their curls beneath a leaf while an almost fully developed larva waves to the camera while searching for another meal.

As larvae, dogwood sawflies have, quite literally, a colorful juvenile history. After hatching from eggs, larvae are rather translucent yellowish creatures resembling gummy worms. As they develop and molt, specialized glands produce a snowy-white cloak of wax. Fully developed larvae shed the white waxy cloak and assume a dashing color scheme of yellow, white, and black. Why the chameleon routine? Well, some scientists have speculated that the brilliant white coloration and elongated body of young larvae may mimic a bird dropping and reduce the chance of predation. What self-respecting bird eats bird droppings, right? Another hypothesis suggests predators and small parasitic wasps may be unable or unwilling to effectively attack sawfly larvae through their cloak of wax.

Last week while on an adventure along the Patuxent River, I spied what I believed was a larva feeding on a patch of dastardly stilt grass. Delighted that something might be eating this aggressive invader, I investigated the critter and was disappointed to find nothing but an empty exoskeleton adorned with tufts of fluffy wax. Above the stilt grass towered a lovely black walnut tree whose leaves were disappearing down the gullets of another sawfly known as the butternut woollyworm.  Unlike its cousin the dogwood sawfly, this sawfly spends winter as a pupa in the soil enclosed in a durable case. In spring adults emerge and, after mating, females use their saw-like egg-laying appendage called an ovipositor to insert eggs into the mid-vein of walnut leaves. Newly hatched larvae are naked but soon develop a flocculent cloak of magnificent white wax. Upon molting from one instar to the next, this cloak is shed but often remains attached to a leaf for several days or falls on underlying vegetation like stilt grass to fool passing entomologists. In addition to black walnut, Juglans nigra, as their common name implies woollyworms also frequent butternut, Juglans cinerea, and have been reported from hickories, Carya spp. Over the next week or two, be on the lookout for these waxy sawflies on dogwoods and trees in the walnut family. Try to imagine what all the wax is about.  

High in the canopy, butternut woollyworms dine on leaves of a black walnut tree. Although their white waxy mane evokes visages of a shaggy dog or Cousin Itt, the flocculent cloak may dissuade attack by predators or parasitoids. White, waxy filaments dancing in the breeze may not advertise a tasty meal to vertebrate predators accustomed to naked caterpillars for dinner.

 Acknowledgements

This episode is dedicated to our friend Jimmy and in memory of Angela who shared their sawflies and inspired this Bug of the Week. The interesting articles “Be Alert for Dogwood Sawfly” by Joe Boggs, Insects that Feed on Trees and shrubs by Warren Johnson and Howard Lyon, and “Seasonal Cycle and Habits of the Butternut Woollyworm” by L.L. Hyche were consulted in preparation of this episode.

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In a previous episode of Bug of the Week, we lamented the scarcity of swallowtail butterflies in our gardens. Swallowtails have been scarce, but in my flower beds, bumble bees have been rocking. Bumble bees build nests in the ground, often in the former burrows of chipmunks, or sometimes in the hollow of a fallen tree. One might think a carefully constructed subterranean nest defended by bumble bees would be a pretty safe place to raise young. Most of the time this is true, but not so when red velvet ants are in town. This gorgeous insect is not an ant at all. Ants are social insects ruled by one or more queens governing a caste system of workers. Velvet ants are wasps in the family Mutillidae, a large group of solitary wasps that prey upon ground-nesting bees. We met a fast-moving velvet ant in the caldera of a sleeping Costa Rican volcano in a previous episode of Bug of the Week. The female velvet ant featured this week was discovered dashing about a local landscape. Red velvet ants are reported in most counties in Maryland and in addition to my home in Columbia, I have received images or specimens from Adamstown, Pasadena, Queenstown, and Bowie.  

Velvet ants, including the one we meet today, are part of a large mimicry ring. Bright contrasting colors of dozens of species of velvet ants, including Dasymutilla occidentalis, send a warning to potential predators that an attack will be met with a potent retaliatory response, a wicked sting. The easily recognized shared appearance of so many species of velvet ants is called Müllerian mimicry, first proposed by famed German naturalist Fritz Müller. Although lacking wings, the velvet ant is no slow poke. She runs like a demon while searching for a nest of unsuspecting bumble bees. Her powerful jaws and terrible stinger probably allow her to fight her way past bumble bee defenders and enter the brood chamber of the bee hive. In the brood chamber, bumble bee larvae are nourished and cared for by bee workers. The velvet ant lays a single egg on or near the bumble bee’s babes. This egg hatches into a velvet ant larva that consumes a developing bee. When fully developed, the wasp larva forms a pupa and later emerges as an adult velvet ant. Although female velvet ants are wingless, male velvet ants have wings that are shiny and jet black. The males fly about in search of flower nectar, pollen, and mates.  

It’s been a good year for bumble bees in my garden, working the blossoms and returning to nests, often abandoned chipmunk burrows. Elsewhere in the lawn, female red velvet ants prowl, searching for nests of ground nesting bees and wasps. If you see this amazing creature, avoid the urge to pick it up unless you yearn for a very memorable sting.

The lovely female velvet ant in this episode has yet another defense in addition to jaws and stinger. When grasped, she emitted a clearly audible squeaking sound. Squeaking, or stridulation in bug lingo, is a vibration produced by an insect. In this case stridulation occurs on the abdomen where one body part rubs against another. What purpose does the squeaking serve? Along with the bright red and black coloration, the loud squeak probably serves as a warning to any would-be predator that this beauty packs a punch. You see, the other common name for the red velvet ant is “cow killer.” When I grabbed one with a pair of forceps, an enormous, angry stinger emerged from the tip of her abdomen in search of something to punish. Some say that the sting of a velvet ant is strong enough to kill a cow. While this surely never happened, people stung by the velvet ant report a highly painful experience, long to be remembered.   

 Acknowledgements      

 We thank Tracy for the inspiration for this episode and for sharing an image of a beautiful eastern red velvet ant. Dr. Shrewsbury risked an awesome sting while capturing the subject for this episode. The fascinating article “North American velvet ants form one of the world’s largest known Müllerian mimicry complexes” by Joseph S. Wilson, Joshua P. Jahner, Matthew L. Forister, Erica S. Sheehan, Kevin A. Williams, and James P. Pitts, and the buzzy “Bees, wasps, and ants” by Eric Grissell were used to prepare this episode.

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Community gardens are fertile hunting grounds for interesting insects. On a recent visit to the West Side Community Garden in Columbia, Maryland, patches of milkweeds, mountain mints, and monardas were humming with pollinators large and small. In addition to the standard bees, butterflies, and flies, a couple of very impressive black wasps were busy in the florets. These were not social wasps like Asian giant hornets, European hornets, bald faced hornets, and yellow jackets, all colonial wasps that live in a nest ruled by a queen. These were solitary wasps, a part of the digger wasp clan. The larger of the two, Sphex pensylvanicus, goes by the name of great black wasp, while its smaller orange-legged cousin, Sphex nudus, is known as the katydid wasp.

As members of the digger clan, female great black wasps and katydid wasps excavate galleries a foot or more deep in the soil. This crypt will serve as the nursery and larder for the developing wasp larvae.  Female Sphex wasps search the treetops for those beautiful and melodious nighttime troubadours, the katydids we met last week. Once she locates her prey, she stings and transports her prize back to the subterranean burrow. Inside the burrow she provisions each brood cell with two to six victims and lays an egg on the underside of one katydid. Here is where this macabre tale gives me the willies. The katydids in the crypt are not really dead. They are just mostly dead, like the tortured Dread Pirate Roberts in the movie Princess Bride. Ah, but there will be no Miracle Max to rescue these unfortunate creatures. The venom of the great black wasp does not kill its prey; it merely paralyzes the victim. The moribund katydids are alive but cannot escape the jaws of the wasp larva as it proceeds to consume the hapless prey one by one over the span of about ten days. Whew, makes me glad I am not a katydid. Fully developed larvae spin cocoons in autumn and remain underground through winter, awaiting the return of summer before emerging from the earth to sip nectar and hunt katydids, crickets, and grasshoppers.

Sphex wasps are very fond of mountain mint and spotted horse mint. When the wasp probes the blossom for nectar, anthers dip down and release their pollen on its back.

One of the most curious pollination events takes place as great black wasps nectar at spotted beebalm, a.k.a horsemint (Monarda punctata), one of my favorite flowering plants by virtue of the vast number of insects it attracts. Unlike open-faced flowers such as sun flowers, horsemint provides a curious array of petals, anthers, and stigmas. Nectar fiends like the great black wasp land on petals and, as they probe deeper into the flower, pollen laden anthers dip down and discharge their yellow pollen grains onto the back of the wasp. As the insect moves from floret to floret pollen accumulates, turning the back of the great black wasp yellow. The transformation of the great black wasp to the great yellow-backed wasp never fails to amuse me. Spotted horse mint will always have a place in my garden.

Acknowledgements

The fascinating article, “The life-history and habits of the digger-wasp Ammobia pennsylvanica (Linn.)” by John A. Frisch was used as a reference for this episode. Bug of the Week thanks Dr. Shrewsbury for providing the inspiration and image for this story.

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