Eyespots on the wings of Polyphemus might startle a would-be predator. M. J. Raupp
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.
The beautiful Polyphemus caterpillar is one of the largest caterpillars in North America M.J. Raupp
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.
Amidst a colony of brown ambrosia aphids death awaits in the from of predatory midge larvae of Aphidoletes aphidomyza. These fierce mini-monsters may consume dozens of aphids during their development. Circles mark the locations of predatory midges. Photo by Paula Shrewsbury
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.
Adult predacious midges are small delicate flies resembling their cousin, the boxwood leafminer. Photo by Mike Raupp
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.
Amidst a horde of brown ambrosia aphids, a syrphid fly larva attacks its next victim. M. J. Raupp
One of the best performers in my flower bed is a raucous native plant known as cup plant, Silphium perfoliatum, a premier attractor of insects to the garden. Extravagant floral displays provide nectar and pollen to wide variety of flies, bees, butterflies, and wasps. Nutrients coursing through vascular vessels support several species of sucking insects including leafhoppers, treehoppers , and aphids. And where there are abundant juicy prey items, there are predators, lots of them. During spring and early summer, populations of brown ambrosia aphids have exploded on my cup plants. Like many of their kin, in spring and summer these gals are parthenogenic. They are an all-female society reproducing without the assistance of males. As aphids feed, they excrete a waste product called honeydew. Honeydew contains volatile organic compounds (VOCs), the aromas of which act like a dinner bell ringing “come and get it”. The more aphids and honeydew on a plant, the more likely it will be discovered by flower flies. Once the infestation is detected, the females fly lays a small white egg near the colony of aphids. The egg hatches into a wriggling larva (a.k.a. maggot) whose sole purpose is to hunt and eat soft-bodied prey. With no true eyes, this blind assassin discovers its victims by swinging its head to and fro, searching for prey with sensory structures located on the front end of its fleshy head. When it bumps into an aphid, the flower fly larva snares the aphid with its mouth hook [it looks like Captain Hook’s hook]. Mouthparts pierce the aphid’s cuticle, and the larva sucks the aphid’s blood.
When in bloom, cup plants are dynamite attractors of pollinators. But pre-bloom, cup plants often generate fantastic populations of brown ambrosia aphids. Volatile odors released by the aphids serve as a dinner bell for squads of hungry predators and parasitoids. Not long after aphid populations exploded, adult flower flies deposited eggs near colonies of aphids. From these eggs hatched fierce larvae laser focused on hunting and eating aphids night and day. Watch as one of these tiny terrors makes short work of a misguided aphid. The flower fly larva snares the aphid with its mouth hook. It looks like Captain Hook’s hook. It then pierces the aphid and sucks out its blood. Flower fly larvae make short work of aphids on plants. Along with gangs of spiders, lady beetles, lacewing larvae, predaceous midge larvae and parasitic wasps, aphids on my cup plants will soon be history.
It’s easy to see why another name for the flower fly is hover fly. Flower flies deposit white eggs like these near colonies of aphids. Eggs hatch and blind flower fly larvae hunt by casting their head two and fro. Prey like this aphid are snagged with a mouth hook. Once captured the contents of the aphid are consumed. Sometimes hapless aphids blunder into fly larvae. You can see the dorsal heart of the larva beating as it feeds. Little wonder that aphid populations can collapse when flower flies and other predators and parasites arrive.
Flower fly maggots have prodigious appetites. In the laboratory, I have watched these predators consume more than 25 aphids in a day. Reports of aphid carnage in the literature puts the casualty figures at more than 200 aphids during development for each maggot. In some agricultural systems, flower flies are believed to provide 75% to 100% control of aphids. In my experience with aphids, flower flies, with a little help from lady beetles and other predators, can entirely wipe out populations of aphids in a matter of weeks. So, before you reach for the aphid spray, carefully look to see if the maggot brigade and company are at work. While the brown ambrosia aphids put a minor beat down on my cup plants, they are generally good news for my garden. The aphids have become a factory for many species of predators including spiders, lady beetles, lacewing larvae, predaceous midges and parasitic wasps that will move to other plants in my landscape once the brown ambrosia aphids are kaput, all part of Mother Nature’s plan for a more sustainable landscape.
This little Cycloneda lady beetle has her jaws wrapped around a juicy brown ambrosia aphid. M. J. Raupp
Acknowledgements
We thank Dr. Jeff Shultz for identifying the cool male lynx spider and Dr. Paula Shrewsbury for planting silphium, identifying the pretty polished lady beetle and providing inspiration for this episode. The fascinating account of defensive behaviors in aphids entitled “Collective Defense of Aphis nerii and Uroleucon hypochoeridis (Homoptera, Aphididae) against Natural Enemies” by Manfred Hartbauer was consulted to prepare this episode.
The underside view of an adult firefly reveals the whitish light organs where photocytes, cells that produce light, are located. Large eyes help fireflies find the glow of mates at night. M.J. Raupp
Happy 20 years Bug of the Week
This June marks the celebration of 20 years of Bug of the Week. We want to thank all our viewers in more than 200 countries worldwide for your continued support. Last year we set a record with more than 370 thousand visits. Thank you so much. This week we call on one of Mother Nature’s most fabulous creations to help us celebrate. Three cheers for fireflies.
Much of this episode comes courtesy of Dr. Paula Shrewsbury, Entomologist at the University of Maryland, College Park, who created this great article for her “Beneficial of the Week” in the IPM Alerts – Landscape & Nursery.
“I saw my first fireflies of the season in Sharpsburg, MD on May 17th; and this week I saw fireflies flashing in Columbia, MD. It looks like it is going to be another good year for fireflies based on the amazing display of flashing lights so far.
Fireflies, also known as lightening bugs, are really neither bugs nor flies. They are characterized as soft-winged beetles in the order Coleoptera and the family Lampyridae. There are over 2,200 known species of fireflies, of which about 165 species have been reported in the U.S. and Canada. Fireflies are found in temperate and tropical regions and in the humid regions of the Americas, Asia, and Europe. In the U.S., the abundance of fireflies is greater east of the Great Plains than in western states. Interestingly, fireflies that produce light are uncommon in western North America. Some firefly species are diurnal, and therefor have no need to create light. These species are known as daytime dark fireflies and they use chemical pheromones for mate attraction. Although the adults do not light, the larvae do glow at night, similar to eastern species.
Most flashing species occur east of the Mississippi River, are about ¾” in length and are active at dusk and night. Adults and larvae of many firefly species exhibit bioluminescence – they glow in the dark! Many organisms such as bacteria, fungi, jellyfish, algae, fish, clams, snails, crustaceans, and of course insects [including some click beetles] exhibit bioluminescence. Firefly species have special light organs that make the underside of their abdomens light up.
To help celebrate twenty years of Bug of the Week, let’s enjoy one of Mother Nature’s finest light shows courtesy of fireflies. How do they produce light? See the white segments at the tip of the firefly’s abdomen. These segments contain photocytes, cells that produce light. I asked this little guy to show off his stuff. Look at him go. Don’t worry, he was released nonplused but unharmed. Male fireflies perform aerial displays to impress females watching from vegetation on the ground or on branches. If the she firefly likes the performance, she may signal back with her flash. Watch as a male firefly searches for his mate on a cluster of leaves. Eventually he finds her and their union is consummated. During June and July, take a moment at twilight to visit a lawn, meadow, or park to enjoy these beautiful and illuminating creatures.
How do fireflies make light? The light emitted by a firefly is actually a chemical reaction in the beetle’s abdomen. The light organ has special cells that contain a chemical called luciferin. An enzyme called luciferase combines oxygen with luciferin in these cells to create light. Scientists actually do not know how fireflies regulate their lights to turn them on and off. You might have also noticed how “cold” the light looks. This is because no infrared (or heat) or ultraviolet frequencies of light are emitted. Among the light-producing fireflies, lights are yellow, green, or pale red.
Firefly larvae called glow worms have luminescent organs on the underside of their abdomen. M. J. Raupp
Why do fireflies bioluminescence? The purpose of this bioluminescence varies. It is believed that the flashes are part of a signaling system for attracting mates. Both males and females emit light intermittently or in specific flash patterns. The rhythmic flash patterns produced are specific for each species of firefly and vary by sex within a species. The flashes that we see are from the males that are attempting to attract a mate. For example, males of the common eastern firefly (Photinus pyralis) flash every six seconds. Females watch the light “show” and if a display from a specific male is particularly attractive, she will flash a response but only if it is from the male of the same species. The male descends to that location to mate with her. In addition to transferring sperm to the female during copulation, the male offers a nuptial gift of rich protein, which the female uses to provision the eggs that will soon start to develop in her ovaries. Interestingly, in one species of firefly, Photuris pensylvanica, the female mimics the flash pattern of another species, Photinis pyralis, to attract the male of the other species to her. When the male of the other species arrives thinking, he has found his mate – she eats it to obtain defensive compounds used to protect her eggs. A bad surprise for that male.
Why are fireflies considered beneficials? Well, the soil active firefly larvae or glow worms are voracious predators of soft-bodied invertebrates and known to feed on slugs, snails, worms, and other soil-dwelling insects. Glow worms use their mandibles to inject prey with a paralyzing neurotoxin, making it defenseless, and then secrete digestive enzymes that liquify the prey making it easier to consume. Firefly larvae or glow-worms are believed to glow as a warning signal telling predators not to eat them as they are mildly toxic and taste nasty. It is not well known what all adult fireflies feed on but some feed on pollen and nectar and some are reported not to feed at all.
A pair of firefly larvae snack on a hapless earthworm. M. J. Raupp
Although the larvae of fireflies are referred to as glow-worms, technically this is not quite correct. Glow-worms are a type of firefly where the adult female is flightless and maintains the appearance of a larva and she emits a long-lasting glow, similar to larvae. The males have the appearance of an adult firefly. To make it more confusing, other insect larvae that glow, are sometimes called glow-worms too. Since most fireflies that produce light are in the Eastern U.S., it makes the nightly light shows we encounter here something special to behold for a few weeks during spring and early summer. Be sure to help young people you know, and others, enjoy the experience of observing and collecting fireflies. Be certain to release the little lights when you are done!”
Light pollution and fireflies
Over the past few years, many have been concerned about dwindling numbers of lightning bugs in our region. While hard data on this issue are difficult to come by, one important study conducted by scientists at the University of Virginia suggests that light pollution caused by brightly lit homes and buildings has disrupted the normal ecology and behavior of these remarkable creatures. By adding artificial light to nocturnal courting grounds, normal courtship behaviors and mating success of fireflies were compromised. The authors suggest these reductions in mating success could lead to fewer fireflies in locations with light pollution. The development of natural areas and destruction of habitat are also thought to contribute to reductions in firefly populations. Others believe that widespread use of residual insecticides to treat lawns may have contributed to the lightning bug’s decline. Perhaps unfavorable weather cycles or a dearth of food for predatory lightning bug larvae, which live on the ground, may have suppressed their numbers in years past.
What can be done to help our fireflies and other nocturnal insects? Reducing sources of artificial light at night (ALAN) by using motion detectors to trigger security lights, timers and dimmers to regulate intensity and timing of illumination and simply turning off unnecessary lights can help. Outdoor lighting along pathways can be shielded from above to reduce light scattering that might attract flying insects. To learn more about light pollution and some solutions to ALAN, visit DarkSky.
During these glorious days of June and July, take a moment at twilight to visit a lawn, meadow, or park to enjoy these beautiful and illuminating creatures.
Acknowledgement
Bug of the Week thanks all our viewers over the last two decades. Our F2s, Eloise, Abby, and Jackie provided the inspiration for this episode and Dr. Shrewsbury provided much of the cool content. The interesting articles “Experimental tests of light-pollution: Impacts on nocturnal insect courtship and dispersal” by Drs. Aerial Firebaugh and Kyle Haynes, “Flash Signal Evolution, Mate Choice, and Predation in Fireflies” by Sara M. Lewis and Christopher K. Cratsley, “Silent Earth” by David Goulson, and fascinating studies of Dr. Sara Lewis and Dr. Thomas Eisner and their colleagues, served as resources for this Bug of the Week.
Meet the royals. The smaller king is on the left and his queen on the right. During her reign as queen, which may be decades, she will lay hundreds of thousands of eggs. Photo credit: Dr. Barbara L. Thorne (copyrighted)
A neglected bag of mulch is a great place to raise a colony of termites.
A couple of weeks ago I went to the back yard to dispose of an unused bag of mulch near my woodshed. Upon lifting the bag, I discovered my tardiness created the perfect home for a colony of eastern subterranean termites. These ubiquitous rascals set up shop beneath the mulch bag, dining on chips of wood leftover from my wood-splitting efforts. They also dined on delectable morsels of cellulose and lignan in the mulch within the plastic bag. In addition to large-headed, large-jawed soldiers and diminutive workers, dozens of winged reproductives were ready to take flight on their mission to found new colonies. Termites are regular visitors to my landscape. Several years ago, on a sunny spring morning with the air temperature hovering in the 70s, I was treated to a full-blown termite swarm. The wooden risers of ancient garden steps were home to a massive termite colony. Over several hours, thousands of adult reproductive termites issued forth and took wing, fluttering off to establish colonies of their own.
Here’s a recipe for making termites. Buy one bag of mulch in autumn and place it on the ground near the woodshed where there are lots of wood chips. Let it rest undisturbed for six or seven months. When temperatures climb into the 70’s in April, turn it over and enjoy plenty of workers and dozens of winged reproductives ready to fly off and establish new colonies. Why, you can even find them inside the bag of mulch.
Termites are remarkable creatures with the ability to perform a digestive magic trick unparalleled in the human world. They consume wood. To utilize nutrients tied up in a biopolymer hard enough to dull an axe blade, most termites rely on symbiotic bacteria in their gut to digest the rugged plant material called cellulose. Some primitive species of termites enlist unicellular organisms called protozoa to accomplish this feat. Termites have an unusual and rather crude way of passing these vital microbes from one termite to the next. They employ a process known as proctodeal trophallaxis. One termite excretes a droplet of microbe-packed fluid from its anus. This packet of goodies is consumed by another termite waiting at the rear end. Yum! In addition to the transfer of vital symbionts from one termite to the next, trophallaxis is also a way of disseminating chemical messages called pheromones that regulate the development and behavior of termites within the colony.
Eastern subterranean termite soldiers have enlarged heads with powerful jaws. A tiny newly molted worker nymph is overshadowed by the huge soldier.
Termites are part of an elite group of social insects that include ants, bumble bees, honey bees, and yellowjackets we met in previous episodes of Bug of the Week. Social insects such as termites have a distinct division of labor with a caste system that includes specialized workers, soldiers, and reproductives. Workers are the most common caste in the subterranean termite colony. The primary tasks of these cream-colored laborers are to consume and process wood, seek new resources, construct galleries, build foraging tubes, and care for the young and reproductives. As the name implies, soldiers are tasked with colony defense. They are easily recognized by their enlarged heads with powerful darkened jaws. Depending on the species, soldiers are armed with jaws that stab, cut, or snap and whack an enemy. Termite reproductives are called kings and queens. As light-colored juveniles in the colony, they pass through a developmental stage called the nymph and are distinguished from workers by developing wing buds found on the thorax just behind the head. When they molt to the adult stage to become males (kings) and females (queens), their cuticle tans to dark black. This tanning process allows them to retain body moisture as they exit the damp earth and enter the drier world above ground.
Who’s filling the air around my home on a sunny spring morning? Why, thousands of reproductive termites spawned from wooden steps in my backyard. Watch as they issue forth from gaps in the wood and mount vegetation to take flight. Can you count how many there are?
During spring and summer in the DMV, the air can be filled with thousands of termites, known as primary reproductives, swarming to found new colonies. But the world above ground is treacherous and only a few of the thousands that emerge live to establish a new colony. After landing at a new site, wings are no longer needed, and kings and queens will quickly shed their wings by snapping them off with quick twists and turns of their body. Hopeful males frantically pursue potential mates and the lucky ones that succeed in the mating game help their queen establish a colony. Queens of some species may live more than 40 years and produce more than 20,000 eggs per day. Eggs hatch and develop into workers, soldiers, and new reproductives. In addition to primary reproductives, termite colonies may also contain light colored secondary reproductives lacking wings that develop directly from nymphs, and tertiary reproductives that develop directly from workers. This remarkable system of reproductive redundancy undoubtedly contributes to the longevity and success of a termite colony.
After taking flight and landing at a new colony site, a female termite snaps-off her wings and is quickly pursued by a hopeful suitor.
In the natural world, termites live in subterranean nests, foraging on fallen trees. But with the advent of domestic structures, they often colonize dark interiors of floor joists and paneling within our home if conditions of moisture and temperatures suffice. They reach the structural wood of our buildings by constructing tunnels of soil, wood, saliva, and excrement from an outdoor colony like the one in my flower bed, up foundation walls until they reach the wood of a sill plate or floor joist. There they enter the home. If wood is sufficiently moist, let’s say it is due to a leaky pipe, plugged gutter, or cracked foundation, termites can set up shop inside your home. The appearance of swarming winged primary reproductives inside your home is a sure-fire indication of an infestation. To learn more about the biology and management of termites in and around your home, please visit the following excellent website:
Two great books, “The Insect Societies” by E.O. Wilson and “For Love of Insects” by T. Eisner, were used as references for this Bug of the Week. Bug of the week thanks Drs. Barbara Thorne and Nancy Breisch for assistance in creating this episode. All images and videos at Bug of the Week are copyrighted and may not be reproduced without permission.
On warm nights in late winter and early spring, Ophioninae wasps are regular visitors to my porch light.
The return of some delightful 70-degree weather last week heralded the return of lovely parasitoid wasps in the subfamily of Hymenoptera known as the Ophioninae. Each year we welcome these nocturnal visitors to my porch light as one of the harbingers of spring. They regularly appear on the first 60-ish degree evenings in March at my porch light. This year I discovered my first one last week on a windowsill near my houseplants. The mystery of how it got into the house remains unresolved, but we were still delighted to greet it.
Beneath the glow of my porch light, an Ophioninae wasp grooms its antenna and then taps its front foot in time with the music.
A beautiful ichneumonid wasp rests on the chrysalis of a swallowtail butterfly from which it emerged.
Ophioninae wasps belong to a large and important family of membrane-winged insects known as ichneumon wasps. Ichneumon wasps perform the important ecosystem service of biological control by parasitizing some of our most important pests, including corn earworms and white grubs. However, they also attack other non-pestiferous insects including the larvae of butterflies. Some years ago, we collected a beautiful caterpillar, the larva of the tiger swallowtail butterfly. After eating leaves like a ravenous teenager, it formed a remarkable chrysalis resembling a dead leaf. We placed the chrysalis in a terrarium and anxiously awaited the appearance of a beautiful swallowtail butterfly. Events took an unexpected turn when a feisty looking wasp emerged from the chrysalis instead of a gorgeous butterfly. You see, unbeknownst to us, prior to the capture of the swallowtail larva, a parasitoid ichneumon wasp had visited it. The female ichneumon wasp likely grappled with the caterpillar before stinging it and depositing an egg within.
The fascinating part of this story is that the parasitoid inside the swallowtail did not immediately develop and emerge from the caterpillar. This clever parasitoid waited for the caterpillar to feed and grow before beginning its own development. The tiny invader then completed its development and emerged as an elegant ichneumon wasp. Parasitoids with this type of delayed development within a host are called koinobionts. Many species of koinobionts synchronize development with that of their host by responding to changing levels of hormones produced by their host during growth and development.
Ichneumonid wasps can be a little testy when sharing a droplet of honey.
The humongous ovipositor on this ichneumon wasp in the genus Megarhyssa is used to drill beneath the bark of tree to deposit an egg inside a larva developing deep within the wood.
Returning now to the present, if you would like to see ichneumonid parasitoids, switch on your porchlight on a warm spring evening, and see who arrives. Don’t be surprised if several pale orange Ophioninae ichneumons appear. If you dare, do as we do and invite them in for a drink. As you see in the video, a little honey and water seemed just the right tonic for these busy parasitoids. After they had their fill, we bid them adieu and returned them to the wild. Perhaps my hospitality will be rewarded in a few weeks by these ichneumons in the form of koinobionic attacks on the pesky caterpillars and white grubs that perennially plague my flower beds.
Acknowledgements
The fine references “The Insects: an outline of entomology” by P.J. Gullen and P.S. Cranston, and “Subfamily Ophioninae” by I.D. Gauld and D.B. Wahl, were used as references for this Bug of the Week. Thanks to Dr. Shrewsbury for spotting the Ophioninae wasp which was the inspiration for this episode.
Children of all ages will have a great time at the Maryland Day Insect Petting Zoo.
The lovely lubber sports multiple defense techniques.
One of the joys of spring is observing the antics of insects and their relatives as they resume their activities outdoors. To celebrate this annual renaissance, the Department of Entomology hosts an award-winning Insect Petting Zoo as part of the Maryland Day Gala at the College Park Campus of the University of Maryland on Saturday, April 26, from 10 am to 3 pm. The Insect Petting Zoo is in the Plant Sciences Building on the ground floor directly across from Regents Drive parking garage.
Come to the Insect Petting Zoo, Saturday April 26 at the University of Maryland, College Park. Travel around the world to meet rocking Vietnamese walking sticks and giant Australian walking sticks pretending to be dead leaves. Amazing Malaysian leaf insects will try to fool you and watch out for the whip scorpion and its smelly surprise. Hold a giant tarantula if you dare, and look at, but don’t touch, the black widow spider. Meet the deadliest creature on our planet, blood-thirsty mosquitoes, and pet a friendly, furry Eastern tent caterpillar. Fast moving green tiger beetles will prowl their cage while blue death feigning beetles will be stuck in second gear. Learn why carpenter bees make holes in your deck and why iconic honeybees and their kin are imperiled in our rapidly changing world. Hope to see you at Maryland Day.
Is that a leaf or a leaf insect? Come to the Insect Petting Zoo at Maryland Day to find out.
This year’s petting zoo will feature an incomparable ensemble of friendly, ferocious, and creepy crawly creatures. A visit to the petting zoo is sure to delight insect aficionados of all ages. This year’s extravaganza features bugs from around your home and around the world. Giant Lubber locusts straight from the Everglades of Florida will reveal their favorite delicacies and how they defend themselves from being eaten. Vietnamese and Australian walking sticks are true masters of disguise and giant Madagascar hissing cockroaches will blow your mind with their size and agility. Watch out for the Whip Scorpion that has a clever trick up its sleeve, or should we say its tail, to thwart attacks by enemies. If you are lucky, you might catch a glimpse of a Black widow spider with a bright red hourglass tattooed on her abdomen, a ferocious Green Tiger beetle hungry for fresh meat, or a Carpenter bee buzzing about its cage. The arts of trickery, mimicry, thanatosis, and other feats of deception and disguise will be revealed by Blue Death Feigning beetles, the European sowbug (roly – poly), darkling beetles (armored stink beetle), the remarkable, petite orchid mantis, and strange leaf insects.
The Spotted Lanternfly is a beautiful insect, but a dastardly plant pest and nuisance in your landscape.
The Insect Zoo is not just a treat for the eyes. Children of all ages will have the chance to hold and touch (with parental permission of course) a multi-legged millipede from the desert or a hairy Eastern tent caterpillar from a cherry tree. The very brave may even have a chance to hold a giant tarantula. If touching isn’t your thing, then you can listen to the buzzing of a bee or the hissing of a cockroach from Madagascar. Meet face to face the number one killer of humans on the planet – dreaded bloodthirsty mosquitoes. Curious smells are on the menu as well. Learn what unwelcome house guests have the aroma of cilantro and discover an arachnid with the pungent odor of vinegar. If you are feeling sociable, investigate the wonders of perhaps our most important social insect, the honeybee. Stop by the invasive species corner and meet dastardly Emerald Ash Borers, the nefarious home invader Brown Marmorated Stink Bug, and the newcomer in our region, Spotted Lanternfly.
Children can collect insect stickers and the first 600 visitors may take home a Terrapin Lady Beetle to release in their garden to put a beat-down on insect pests lurking there.
Don’t miss The Swamp – If you enjoy the life aquatic, be sure to stop by The Swamp across the hall and learn how dragonflies capture their prey and how diving beetles extract oxygen from water.
So, come one, come all to explore Maryland Day and the Insect Petting Zoo!
Bug of the Week thanks Dr. Paula Shrewsbury for organizing the Insect Petting Zoo and Dr. Bill Lamp and his crew for organizing The Swamp at Maryland Day. Special thanks to Todd Waters and Chris Sargent for making our arthropods the happiest six and eight- legged creatures on the planet.
Next time you are dodging carpenter bees, take a moment to check out their head. I’ll bet you will find a white patch on its face between its eyes, the hallmark of the male carpenter bee.
A week or so ago, during a Q and A session at a meeting, I was asked by one nature enthusiast why large black bees were bombarding him in his back yard. Without fail, about this time each spring humans who venture too near a child’s wooden play set, wooden benches or railings, mailbox posts, decks, or houses with cedar siding are divebombed by territorial male bees. The bees have nothing against humans. They are simply jealously guarding potential wooden nest sites from interlopers. Interlopers include other male carpenter bees or almost any other creature that comes into range, including humans.
Wooden structures like this play set bear telltale damage as woodpeckers search for carpenter bees inside the wood. Male carpenter bees zoom around nearby sensing that nubile female bees will soon emerge from these galleries. They divebomb other competing males and nosy humans, aggressively defending their mating territory. When females emerge, they will quickly be mated by diligent guy bees patrolling nearby. Once inseminated, females build new galleries in wooden structures creating nesting sites for their young.
On the outside of a piece of wood all you see of the carpenter bee’s handiwork is a perfectly round hole.
Why do they do this? Here’s the deal. Female carpenter bees build galleries in wooden structures to serve as nurseries for their young. Male carpenter bees go to great lengths to convince potential mates of their worthiness by selecting and defending prime nesting sites. When other male carpenter bees approach defended territories, remarkable aerial battles ensue. Swooping, grappling, and biting often result in both combatants tumbling to earth before one withdraws from the fray. I watched one victorious male guard a nesting site and soon a lovely and somewhat coquettish lady carpenter bee arrived. She rested on the wooden bench guarded by her suitor and a short but energetic romantic interlude ensued. As far as I could tell, the male flew off somewhere, perhaps for more battles or romantic conquests, but the female bee had different matters to attend. After mating, the she bee begins the task of excavating a hole in the wooden structure to be used as a nursery for her brood. Her powerful mandibles create a slightly oval to almost perfectly round hole as she penetrates the wood to the depth of about a half inch. She then makes a right angle turn and continues tunneling parallel to the grain of the wood excavating a series of brood-cells in a linear tunnel. In a piece of wood removed from one of the benches, I observed several tunnels more than a foot in length, some of which branched into secondary galleries. Each tunnel contained as many as thirteen individual brood-cells.
But on the inside, you can see a gallery of brood chambers carved into the wood by the mother bee for her babies.
To construct each multichambered gallery represents more than a month’s worth of chewing and one has to admire the determination of these industrious gals in excavating a home for their young. After the chambers are built, they are meticulously cleaned and filled with bee bread, a nutritious mixture of pollen, nectar, and secretions from glands on the female’s body. Bee bread serves as the food for the young carpenter bees. Starting at the end farthest from the entrance the female deposits an egg in each brood-cell. Each egg hatches into a legless larva that eats bee bread and develops during the course of spring and summer. In brood-cells furthest from the entrance, older larvae complete development first, pupate, and then after emerging from the pupal case in late summer these new adults push their way past brothers and sisters to escape the gallery and search for nectar and pollen. As summer wanes and autumn waxes, newly minted bees forage during the day and return to their galleries to spend the night. With the end of blossoms in the fall, carpenter bees return to their snug tunnels to chill out until the following spring, protected from the ravages of winter.
On a chilly dewy morning in spring don’t be surprised to see a male carpenter bee (left) and a female carpenter bee (right) resting on a flower head.
In locations where carpenters are present, watching humans duck and cover is almost as entertaining as watching aerial battles among male bees. Male bees lack stingers and although the gals are equipped to sting, I have never been stung by one nor have I heard of anyone who was harmed by these fascinating creatures. Carpenter bees do cause some damage to wooden structures. And once woodpeckers find a structure housing carpenter bees, they get busy and can do some remarkable destruction as they peck holes in the wood searching for carpenter bee babies for dinner. Nonetheless, these entertaining native bees provide important services by pollinating our trees, shrubs, and crops.
At past events such as Maryland Day at the University of Maryland at College Park, which will be held on Saturday, April 26 this year, a thousand or more people visit our Insect Petting Zoo. At the zoo our resident carpenter bees receive much interest and attention. In years past, several children and a few courageous adults held male bees and were fascinating by the buzzing sounds and vibrations generated by flight muscles that power their wings. In discussing the antics and activities of carpenter bees, I was heartened to learn that most folks take a “live and let live” approach to dealing with the carpenters. As one lady put it, “This is their world too, you know.” I do know, and well said.
Acknowledgements:
Special thanks to Frank Bruno and the folks at the Howard Conservancy who served as the inspiration for this episode. “Bionomics of large carpenter bees of the genus Xylocopa” by Gerling, Velthuis, and Hefetz” was used as a reference for this Bug of the Week.
Almost-ready-to-emerge cicadas like this one lack dorsal black patches behind their red eyes.
In the past month, we explored the questions of how to know where periodical cicadas of Brood XIV might be seen, how to protect your trees from cicada damage and whether or not we should be worried about being bitten or stung by cicadas. Recently, one of the most frequently asked questions about periodical cicadas is, “when will cicadas appear?” Bug of the Week has been tracking the life history of periodical cicadas for almost two decades, so let’s look at some historical data and see what it reveals.
The “when” question will often be answered with, “when soil temperatures reach 64 degrees Fahrenheit.” This answer comes from brilliant work performed almost 60 years ago by J. E. Heath who discovered that cicadas emerged when “soil temperature at 20-cm depth in seven locations averaged 17.89 C … regardless of date.” This answer holds fairly well even to this day. However, it is not always possible to know just when the magical 64 degrees at 8 inches below ground hits. We explored this in a slightly different way by observing the emergence of straggling Brood X cicadas in the DMV in 2020. In 2020, several locations reported sightings of impressive numbers of Brood X cicadas that appeared one year early. These cicadas are known as “stragglers”. Stragglers are periodical cicadas that emerge years prior to or after the major portion of their brood mates. Often, 17-year cicada stragglers emerge four years prior to the emergence date of rest of the brood. In 2017, Maryland Brood X stragglers appeared on May 14 in Columbia and Gaithersburg. In addition to emerging four years early, sometimes stragglers emerge one year early and this is exactly what happened in 2020. Using data collected in 2020 from the brilliant Cicada Safari App, the very first cicada out of the ground in the DMV was seen on April 19, just south of Towson, Maryland. This one was an extreme outlier. Cicada emergence really picked up in the DMV on May 14, and by May 24, 25% of emerging cicadas were out of the ground. By May 28, 50% of cicadas had emerged, and just few days later, on May 31, 75% of all cicadas had emerged in DC, Maryland, and Northern Virginia. So, if 2025 is anything like 2020, or previous years for that matter, cicadas will be regularly seen as a trickle in some parts of their range in late April or early May with a tsunami hitting in the last two weeks of May and early June as these teenagers are up and out for the Cicadapalooza. Here in the DMV in 2020, the last cicada to emerge was reported in mid-June. Due to a normal life span of two to four weeks, don’t be surprised to see adult cicadas alive and well into the waning weeks of June, but, sadly, in most locations by the 4th of July, their moment in the sun will be all but finished and nothing but a fading memory.
This graph shows the range of cicada emergence dates in Maryland in 2020. These periodical cicadas, early risers of Brood X cicadas called stragglers, emerged one year in advance of their brood mates that appeared in 2021. Note an extremely early riser in April with the vast majority of cicadas emerging in late May and early June.
Unfortunately for most of us in the DMV, cicadas are likely to visit only Botetourt, Lee, Russell, Scott, Smyth, Tazewell, and Wise counties in western Virginia this year, with no hope of seeing them in DC and little hope of a visit in western Maryland. But for other states ranging from Georgia to Massachusetts Brood XIV is expected. Of course, the emergence in Georgia will begin weeks ahead of the emergence in Cape Cod. Back in the days of Brood X in 2021, Georgia reported adults in late April but in northern parts of Brood X’s range in northern Illinois, the adult show didn’t get underway until late May according to iNaturalist.
For seventeen years, nymphs of Brood XIV cicadas have been developing underground. While digging a hole in my yard years ago, I discovered a quartet of periodical cicadas about 14 inches underground. Notice their white eyes and uniformly tan bodies. Here we see a periodical cicada not quite ready to emerge resting at the top of its exit gallery beneath a cinder block. Just behind its red eyes, the dorsal surface of the cicada is uniformly tan. On the evening of its emergence, notice how the dorsal exoskeleton of the fully developed cicada nymph bears two distinct black patches just behind its eyes. I think these are really good clues to help figure out when cicadas are about to emerge in your area.
Note the black patches just behind the head of each cicada on the morning of their emergence.
On a more local level, how can we tell when the big jailbreak is close at hand? The images and video accompanying this episode provide some clues. For weeks prior to emergence, we witnessed almost-ready-to-go periodical cicadas peeking out from their galleries. In these images, notice that just behind the cicada’s brilliant vermillion eyes, the dorsal surface of the cicada’s exoskeleton is uniformly tan in color. On the evening or day of emergence, notice how the exoskeleton of the cicada bears two jet-black patches just behind its eyes. In more than a dozen emergences of periodical cicadas attended by the Bug Guy, this seems to be the clue that cicada emergence is very close at hand or underway. When you see these dark patches, the big show is about to begin. Get ready to enjoy!
Acknowledgements
Three cool articles, “Combining data from citizen scientists and weather stations to define emergence of periodical cicadas, Magicicada Davis spp. (Hemiptera: Cicadidae)” by M. J. Raupp, C. Sargent, N. Harding, and G. Kritsky, “The ecology, behavior, and evolution of periodical cicadas” by K. S. Williams and C. Simon, and “Thermal synchronization of emergence in periodical ‘17-year’ cicadas (Hemiptera, Cicadidae, Magicicada)” by J. E. Heath formed the foundation for this episode.
Cicadas insert soda-straw-like sucking mouthparts called a beak or proboscis into plant tissues to obtain nutrients for growth and development. Adult feeding results in minimal damage to plants compared to injury caused when female cicadas use their ovipositor to slit branches. Into these wounds eggs are deposited in egg-nests. Eggs develop during spring and summer. Cicada nymphs will hatch from these eggs, drop to the earth, and develop underground for the next seventeen years.
In recent episodes we learned where Brood XIV cicadas would and would not be seen this spring. We also discovered what signs to look for in your yard as a presage to their grand appearance. This week let’s tackle a few questions that popped up in a recent conversation with the Weather Channel. Two of the most frequently asked questions regarding cicadas is “do they bite and do they sting?” Well, through my six decades of watching, catching, studying, eating, and photographing cicadas, my answer has been no, don’t worry about being bitten or stung by cicadas. However, following two messages from folks who listened to a television interview this week, I am scratching my head just a little bit about what cicadas can and cannot do with regard to biting and stinging. One viewer recounted an episode almost two decades ago when a cicada landed on their shoulder and pierced the skin leaving behind a zig-zag shaped mark. A second viewer shared an encounter with a cicada that attempted to probe her finger with its beak while she was holding the cicada during a “show and tell” demonstration with some children.
See the black proboscis or beak of the cicada between its front legs? Watch as it pushes its beak into the tree to find the vascular element called xylem which will be its source of liquid food for the next several weeks.
So, let’s dive into these questions about biting and stinging cicadas and see what might be afoot. We all learned in grammar school that one commonality of animals is that they are heterotrophs, that is, they cannot produce their own food but instead must eat other things for their sustenance. And when we think about animals eating, we think about biting, right? Biting usually involves something like what we humans do, jaws with mandibles removing chunks of food. Many insects like grasshoppers, beetles, wasps, and caterpillars have jaws that remove hunks of flesh or foliage as they feed. However, in many clans of insects, these jaw-like mouthparts have morphed dramatically through time into more soda-straw-like mouthparts, called piercing or sucking mouthparts, with the descriptive name of beak or proboscis. The beak has internal channels; one is used to remove liquid food from plants or animals which they feed upon, and another channel is used to inject saliva into the food item. Insects with sucking mouthparts include disagreeable rascals like bed bugs, mosquitoes, stink bugs, and lanternflies. Cicadas also have sucking mouthparts used to imbibe xylem fluid from plants on which they feed. So, do cicadas bite? Technically, you cannot bite with sucking mouthparts but you can suck and yes, cicadas do suck. Obviously, the next question is “do they suck on humans or pets?” The answer as far as I am aware is no. I have never heard of any human or animal losing blood to a sucking periodical cicada. These are obligatory plant feeders. The person mildly assaulted by a cicada shared that it did not break her skin. Also, she disclosed that the cicada had been confined for a long time and maybe it was tired of being held by a human. Who knows?
Young saplings and recently transplanted trees growing rapidly in the open are often heavily damaged by cicadas.
Well, what about stinging? Let’s dive into that. Stinging insects like bees, ants, and hornets, do so with an appendage at the tip of their abdomen called an ovipositor. Queens of these social insects use their ovipositor to lay eggs that hatch into workers. Workers are tasked with the onerous job of defending the colony. The ovipositors of defensive workers are connected to glands that produce venom, powerful chemical cocktails designed to bring intense pain to Winne the Pooh or other interlopers intent on raiding the colony for honey or brood. The ovipositor of most other insects is an appendage used to deposit eggs in a place where offspring can develop and thrive. As is the case with cicadas, ovipositors of these insects lack venom. Periodical cicadas use their ovipositor to cut slits into the tissues of plants, primarily trees and shrubs, where eggs of the next generation of cicadas develop before nymphs hatch and drop to the earth. As you might surmise, these ovipositors are stout and sharp enough to pierce the bark of a branch. Perhaps the person assaulted by a cicada was the unwitting victim of a misguided female cicada who mistook a human shoulder for a place to deposit eggs. Animal behavior is rife with mysteries and evolutionary mistakes, some for the better and some for the worse. If this assault was an attempt to lay eggs in a human rather than a plant, you can bet these foolish egg-laying genes will not last long in the reign of cicadas.
Female cicadas use saber-like ovipositors to cut slits in the bark of small branches. These slits are called egg-nests. Watch as the female cicada moves her ovipositor in and out of an egg-nest where she deposits 20 to 30 eggs. She creates dozens of egg-nests which line small branches throughout the canopy of trees she visits. In some cases, weakened branches break and leaves die, creating so-called “flags” hanging throughout the crowns of cicada laden trees. Young saplings and recently transplanted trees growing rapidly in the open are often heavily damaged by cicadas.
Wrapping trees in netting will prevent periodical cicadas from damaging branches of young trees.
My take is that the chances of being probed by the beak of a cicada or assaulted by a crazed, egg-laying female are very small. However, for the millions of homeowners that might be visited by periodical cicadas there is one potentially significant problem. This “dark side” of periodical cicadas manifests itself if you have small saplings or have recently installed young trees in your landscape. Egg-laying cicadas will slice branches to insert their eggs into egg-nests. This causes the tips of many branches to wither and sometimes die. Dying and dead terminals droop, resulting in a type of tree injury called flagging. Some injured terminals break and fall to the ground. Branches that do not break may eventually heal, but the wound-site may form a gnarly irregular swelling on the branch. Which plants are most likely to be affected? The bad news here is that periodical cicadas are broad generalists. Miller and Crowley (1998) studied 140 genera of trees at the Morton Arboretum and found more than half sustained injury caused by ovipositing females. Among the most severely affected were ones common to landscapes in the DMV, including Acer (maple), Amelanchier (shadbush), Carpinus (hornbeam), Castanea (chestnut), Cercidphyllum (katsura), Cercis (redbud), Chionanthus (fringe tree), Fagus (beech), Quercus (oak), Myrica (bayberry), Ostrya (hophornbeam), Prunus (cherry) and Weigela (weigela). Another study by Brown and Zuefle (2009) of 42 woody plant species added several new genera to the list and found all but 10 species were used by cicadas to lay eggs. Small rapidly growing trees with longer, more open branching habits found in young saplings were more heavily used for egg-laying. Trees at the edges of forests with rapidly growing branches exposed to sunlight often sustain more cicada injury. While ovipositional injury poses a threat to newly planted trees, for older and well-established trees flagging and limb breakage may occur in the short term, however, studies indicate that the long-term threat to tree vitality is minimal (Miller and Croft 1998).
How can you mitigate damage caused by ovipositing Brood XIV cicadas on young trees in your yard? Unfortunately, sometimes our knee-jerk reaction is to grab a can of insecticide and start squirting when we see a bug. In the case of periodical cicadas, studies have shown that the most effective deterrent to egg-laying cicadas is to wrap your saplings in netting that prevents females from laying their eggs. Ahern et al. (2005) found that linden saplings protected by netting with openings of 1 cm (0.4 inches) prevented cicadas from laying eggs whereas saplings treated with systemic insecticides or those left untreated received several hundred egg-nests along their branches.
Young linden trees protected by netting had virtually no egg-nests laid in their branches while those treated with a systemic insecticide or left untreated had hundreds of egg-nests deposited in their branches. Data from Ahern et al. 2005.
In future episodes we will explore when Brood XIV cicadas might appear and learn more about these strange and remarkable insects.
To learn how to properly protect your tree with netting from egg-laying cicadas, please watch this clever video.
Acknowledgements
Great references for this episode include “Does the periodical cicada, Magicicada septendecim, prefer to oviposit on native or exotic plant species?” by W. P. Brown and M. E. Zueffle, “Effects of oviposition by periodical cicadas on tree growth” by K. Clay, A. L. Shelton and C. Winkle, “Periodical Cicada (Magicicada cassini) Oviposition Damage: Visually Impressive yet Dynamically Irrelevant” by W. M. Cook and R. D. Holt, “Effects of periodical cicada ovipositional injury on woody plants” by F. Miller and W. Crowley, “The ecology, behavior and evolution of periodical cicadas” by K. S. Williams and C. Simon, and “Comparison of Exclusion and Imidacloprid for Reduction of Oviposition Damage to Young Trees by Periodical Cicadas (Hemiptera: Cicadidae)” by R. Ahern, S. Frank, and M. Raupp. Thanks to two anonymous viewers who shared their stories with me and to my friends at the Weather Channel for allowing me to share cicada stories with others.
