Murder wasps – time to panic? Asian giant hornet, Vespa mandarinia

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Last week an article in the New York Times set off a firestorm of interest in a fierce predatory hornet that was recently discovered in the Pacific Northwest. By the way, hornets are a type of social wasps that live in colonies with a caste system of queens, workers, and drones. In September of 2019, in the town of Nanaimo on Vancouver Island, a colony of Asian giant hornets (AGH) was discovered and destroyed. Three months later in Blaine, Washington, the first confirmed detection of AGH in the United states was made. Several more potential sightings and suspected attacks on honey bee colonies were reported in Washington State during the latter part of 2019. How AGH arrived in North America from infested nations in Asia including Japan, China, Taiwan, Laos, Thailand, Cambodia, Myanmar, Vietnam, Nepal, India and Sri Lanka, remains a mystery. However, as with recent introductions of other invaders such as spotted lanternfly, brown marmorated stink bug, and emerald ash borer we met in previous episodes, it is probably a safe bet that they sailed across the seas as stowaways in a shipment of goods headed for a port on the Pacific coast. One disquieting aspect of these recent discoveries is evidence suggesting that hornets found in Canada were genetically distinct from those discovered in the US. This opens the door to the possibility that at least two independent introductions have occurred. Not surprising, but not good news.

Let’s take a quick look at four other species of stingers that might be confused with the Asian giant hornet. The Asian giant hornet is large with queens about two inches long. A large yellow head at the front leads a yellow abdomen encircled with several dark bands with even margins. Queens of the next largest hornet, the European hornet, measure just shy of an inch and a half. Heads are chestnut or amber and the abdomen has a few dark bands with strange dots at the posterior margin. The Baldfaced hornet is a native with striking colors of white bands and markings on a black background. Queens are about three quarters of an inch long. Several species of native and introduced yellowjackets sport bold alternating bands of black on yellow. They range in size from about half to three quarters of an inch. The last wasp in this gallery is our native Cicada killer. Commonly seen in summer, these hunters of annual cicadas have a shiny black abdomen with yellow or creamy patches partially encircling the sides. They are quite large at an inch and a half or more.  Image of Asian giant hornet by Allan Smith-Pardo of USDA APHIS PPQ and Bugwood.org; other images and video by Michael J. Raupp.

People have asked why they should be concerned about this invader. Two good reasons exist. First, even though these are not “generally aggressive” towards humans, like other social insects including paper wasps, yellowjackets, and honey bees, they will forcefully defend their colony if the colony is threatened. And their sting really packs a wallop. Descriptions of pain associated with the sting liken it to being stabbed with a hot nail, not something I have experienced but it sure sounds painful. The toxicity of AGH’s venom is actually somewhat less than that of the honey bee, however, due to their very large size, among the largest of all hornets on the planet, the volume of venom delivered per sting is quite large. Many deaths associated with stings from hornets, bees, and wasps result from severe allergic reactions called anaphylaxis. However, reports of human deaths from China and Japan have been linked to the toxic properties of the venom itself when people received multiple stings by many AGHs. The venom of AGH is a witches brew of chemicals, including cytolytic toxins that destroy cell membranes, and neurotoxins that attack the nervous system. One account from China claimed that 41 people had been killed by AGH stings with another 1,600 needing medical attention. To put this into perspective a bit, here in the US the CDC reports on average 62 deaths each year due to stings from hornets, wasps, and bees. And for the major gender demographic of Bug of the Week, the men, about 80% of these deaths are males. Figure that one out.

The second, and perhaps more important reason for concern, is the potential effect AGH can have on the already beleaguered honey bee industry and non-commercial beekeepers. Already imperiled by invasive mites and diseases, climate change, and pesticides, honey bees now face a new enemy. AGH has been described as a specialist predator on social bees including our domestic European honey bee, Apis mellifera. In the typical seasonal progression of business in a colony of AGH, many different types of insects and other arthropods are captured by foraging workers, dismembered, and chewed into balls of flesh. These meat balls are taken back to the colony as food for the queen and developing hornet larvae. In a remarkable treatise on the biology of AGH, Matsuura and his colleague Sakagami described a unique and diabolical attack levied on honey bee colonies that begins in late summer and early autumn. Phase 1 of the attack, called the hunting phase, occurs when individual hornets lurk near a hive, capture and kill singular honey bees, macerate them into a ball, and take them back to their colony to feed the brood. Phase 2, graphically named the slaughter phase, happens when several hornets focus their attention on one beehive. As guard honey bees mount a counterattack to the pillaging hornets, the attackers grapple with the defenders, decapitate them with powerful jaws, and discard their victims in front of the hive. The slaughtered bees are not taken back to the hornet’s nest as a source of food. They are simply discarded on the ground. The slaughter phase can last several hours and decimate a hive. One report of an attack by 30 hornets resulted in the death of 25,000 honey bees. Phase 3 of the attack is called the occupation phase. After the slaughter is complete, with most honey bee defenders dead and most other workers and foragers having abandoned the hive, the killing of adult honey bees ceases. Attention turns to bee brood (immatures) developing in their cells. Asian giant hornets post guards at the entrance of the beehive ready to attack humans or other hornets not part of the same clan that approach the hive. Inside the hive, bee larvae and pupae are pulled from their chambers and transported back to the hornets’ nest to feed developing hornet larvae. This nightmare for honey bees leaves little wonder for why these marauders are called murder hornets.

Should the discovery of AGH on the west coast send shockwaves across our nation? Not at this point in time. The infestation on the west coast at the time of this writing consists of one colony in British Columbia that was completely destroyed last year. While the discovery of hornets and suspected colony raids on beehives nearby portend other colonies of hornets, this season awaits the discovery and confirmation of more established colonies. The critical issues now are to survey, detect, and delimit the extent of this introduction and to act swiftly to eradicate colonies of AGH before this invader becomes well established and spreads. This effort is already underway by agencies and scientists in the United States and Canada. Citizen scientists are being enlisted to help find the hornet and report its location to officials. Past history has proven that very few invaders that arrive on our shores actually become established and achieve significant pest status. Even if AGH were to establish in the Pacific Northwest, it would likely take years if not decades to become broadly distributed across our nation. However, as we have seen with other pests, like emerald ash borer and brown marmorated stink bug, spread of an invasive species can be greatly accelerated by inadvertent human assistance, including interstate transport of materials that may harbor hornets, or arrival of new impregnated queens from Asia that can establish colonies near ports of entry into our country.   

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What should the general public and beekeepers do at this time? Learn to identify AGH and distinguish it from other hornets and wasps. Washington State University and USDA have excellent resources to learn about the biology and management of Asian giant hornet (see the links below). This week’s YouTube video and images should help with identification.

I have received several inquiries over the last week regarding insects thought to be Asian giant hornet. These have all turned out to be European hornets, which are quite common here in the DMV. Check out the image with this story to become an expert at telling these two rascals apart and click on this link to see how European hornets roll.

Please keep your eyes open and if you believe you have discovered AGH, snap a photo with your cell phone and send it to your state department of agriculture or local university extension service. Beekeepers, now is the time to learn about this new threat to your colonies and to learn what steps can be taken should it arrive in your area.  So, is it time to panic? Nah, not here in the DMV for sure; for most of us it is time to become informed about this invader. For beekeepers throughout our country, particularly those in the northwestern United Sates, it is time to be vigilant and learn about the biology and management of this pest.  

Links to other web sites with great information and video of Asian giant hornets include the following:

USDA New Pest Response Guidelines: Vespa mandarinia, Asian giant hornet 

WSU scientists enlist citizens in hunt for giant, bee-killing hornet 

SIZING UP THE ASIAN GIANT HORNET 

Acknowledgements

We thank Kathryn Fink and Celeste Headlee for providing the inspiration for this episode.  We also thank Allan Smith-Pardo of USDA APHIS PPQ and Bugwood.org for the amazing images of Asian giant hornet. “A Bionomic Sketch of the Giant Hornet, Vespa mandarinia, a Serious Pest for Japanese Apiculture” by Makoto Matsuura and Shoichi F. Sakagami, “Purification and properties of a presynaptically acting neurotoxin, mandaratoxin, from hornet (Vespa mandarinia)” by Takashi Abe , N. Kawai, and A. Niwa, “Cardioactive effects of hornet venom, Vespa mandarinia” by T. Abe, and “Giant hornet (Vespa mandarinia) venomous phospholipases” by Takashi Abe, Masato Sugita, Tsuyoshi Fujikura, Jiro Hiyoshi, and Michinori Akasu, provided valuable insights for this week’s episode.

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After a relative lull in activity by eastern tent caterpillars in recent years, they seem to be back with a vengeance this season. So, this week we take a peek into the biology of these leaf-munching tent-makers. Just to avoid a bit of confusion, recall that last autumn we met a relative of the eastern tent caterpillar called the fall webworm, as it constructed massive tents on the tips of branches on a wide variety of trees. This week’s rascal is a creature of spring with a fondness for trees in the rose family like cherry, apple, and crabapple. Several weeks ago when forsythia’s bright yellow blossoms announced spring’s arrival, tiny caterpillars hatched from dark brown, Styrofoam-like egg masses in which they had survived winter’s chill. These egg masses were deposited last summer by female eastern tent caterpillar adult moths on small branches of favored hosts. A single egg mass can contain more than 300 hundred eggs. After hatching, larvae build small silken tents over the egg mass and the surrounding branch. From this bivouac they move along branches, spinning silken threads as they go to mark trails to the newly expanding leaves of their host tree, where they feed. Trail marking chemicals called pheromones are deposited by caterpillars on the silken trail to guide nest mates to the location of delectable leaf clusters. As larvae grow during March and April, they need more room and their silken tents are expanded. Tents are typically nestled in the crotch of large branches or where large limbs branch from the trunk.

The saga of the tent caterpillar began six weeks ago when more than 100 tiny caterpillars hatched from their egg mass. So began the daily ritual of following the silk trail from their tent to a meal of tender young leaves, followed by a return trip to the safety of their tent. Fast forward to last week when almost fully grown caterpillars devoured cherry leaves and beat a hasty retreat to their tent as a wicked rainstorm arrived.

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Eastern tent caterpillars are rather a chummy lot. Brothers and sisters from the same egg mass often participate in group activities such as communal foraging and enlargement of their remarkable tent. Tents help caterpillars conserve heat and enable the writhing metabolic mass of caterpillars to elevate body temperatures for more rapid growth and development during chilly spring days. Their silken homes may also provide protection from predatory or parasitic insects. These hairy caterpillars have a voracious appetite and can strip even large trees of their leaves when many tents are present. After the caterpillars have completed development, a mass exodus occurs from the tree and the larvae wander the land seeking protected spots beneath logs, leaves, stones, and under man-made structures to spin yellowish or white, silken cocoons. The adult eastern tent caterpillars emerge as moths from their cocoons in June or July, mate and lay eggs back on the small branches of rosaceous trees. These eggs house the next generation of caterpillars that will emerge with the bloom of forsythia next spring.

Managing caterpillars

How do you know if eastern tent caterpillars threaten your trees? The best predictor of a problem next year may be the problem you have this year. The images of this Bug of the Week came from a small stand of wild cherry trees that are perennially infested with eastern tent caterpillars. If you currently have eastern tent caterpillars on your trees and you do not intervene, it’s a pretty safe bet that you will have them again next year. Right now as the caterpillars enlarge their tents and move to the crotches of the tree, tents and their inhabitants can be removed with a gloved hand on a cool day, placed in a bag, and destroyed. The old school remedy of “burning them out”, though dramatic, went out with the storming of Frankenstein’s castle. Flames are very damaging to the bark of a tree and should never be used.  

Problems with tent caterpillars in your trees? No worries. Early in the season before eggs hatch, find egg masses on small branches and either crush the egg mass or prune it out and get rid of it. Do the same for small tents later in the season. And if you are really bold, you can simply grab the tent and the caterpillars inside, pull them from the tree, place them in a bag and dispose of them. Boom, problem solved.  

Tall trees festooned with tents may be totally stripped of leaves. While trees may recover and produce a second flush of leaves, repeated defoliation probably reduces the vigor of trees. If you have a tall tree from which you cannot safely remove eggs or tents, you may want to seek the help of a professional certified arborist. If you can’t get around to managing eastern tent caterpillars this season, sometime between August of this year and March of next carefully inspect the pencil-sized branches of your infested trees for egg masses and tiny silken webs. The egg masses are easily removed with a pinch of the fingers or, if you are a bit squeamish about touching bugs, simply get out your nippers prune them out, bag them and then dispose of them. Entomologists believe that eastern tent caterpillar populations run in cycles. After a few years of caterpillar plague, natural enemies such as predators, parasitoids, and pathogens reduce tent caterpillars to innocuous levels. Who knows, perhaps next year Mother Nature will send a tent caterpillar relief package and give our trees a break from these noisome creatures. 

Acknowledgements

The wonderful book “The Tent Caterpillars” by Terrence Fitzgerald, and “Managing Insects and Mites on Woody Landscape Plants” by John A. Davidson and Michael J. Raupp were used as references for this episode.

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A few weeks ago, we visited with pretty ground nesting bees as they built and provisioned subterranean burrows in which to raise their broods. One might think that an underground bunker is a pretty safe place to raise a family. Ah, but a clever beetle lives in the neighborhood of ground nesting bees and targets the bees’ babies as meals for her own young. During the past two weeks, I have seen large iridescent blister beetles patrolling my lawn and lurking near my colony of mason bees. Adult blister beetles are not to be taken lightly by ground nesting bees or by humans. If handled roughly or crushed against your skin, blister beetles release blood laced with potent irritants called cantharidins. They can exude this blood as a potent defense against predators. Upon contacting human skin, these compounds raise nasty looking blisters. Blister beetles consuming plants in meadows have been inadvertently bailed in hay and fed to horses and other farm animals with lethal outcomes.  

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Blister beetles are also the source of the aphrodisiac and medicinal compound called Spanish fly. The term Spanish fly references a particularly beautiful European species of blister beetle, Lytta vesicatoria, from which cantharidins are extracted. Much lore surrounds the use of cantharidins as potions of love, healing, and death. Love potions concocted with Spanish fly are said to be potent aphrodisiacs. One remarkable tale I stumbled across told the story of a gathering hosted by the infamous Marquis de Sade. To liven things up a bit, the Marquis slipped the guests a little Spanish fly on some sweets. Unfortunately, he miscalculated the effective dose and rather than arousing his guests several were poisoned and died. Spanish fly was also used as a medicinal in America’s revolutionary era. The father of our nation, George Washington, had a most disagreeable encounter with Spanish fly. After taking ill, President Washington was near death on December 14, 1799. As was common medical practice at the time, Spanish fly was applied to his neck in an attempt to “draw out” the inflammation. The Spanish fly therapy and four bloodlettings on the same day proved a bit too much for our ailing founding father. He expired.  

Other than packing a nasty wallop of poisons, adult blister beetles live rather placid lives munching leaves or eating pollen. Adult blister beetles consume a wide variety of leafy plants including buttercups, potatoes, mustard greens, beets, and Jimson weed. The larvae of blister beetles are another matter. They are enemies of other insects, including solitary bees such as plasterer bees we met in a previous episode. A sunny backyard hillside sparsely cloaked in grass has become the residence for several species of ground nesting bees at my home. Several years ago, I watched one beetle with a particularly bulbous abdomen spend more than half an hour scooping soil to enlarge a burrow in the earth. When the hole was large enough to accommodate her magnificent rear-end, she turned about and wedged her abdomen into the earth. Although I did not excavate the gallery to confirm what had occurred, according to the literature I am reasonably certain that she deposited her load of eggs into the gallery. When I returned awhile later, she had vanished, having completed her task and carefully sealed the hole with soil.  

The spring crop of blister beetles has arrived and they’ve been checking out my mason bee colony and prowling around my yard. Years ago, I watched a female with an abdomen filled with eggs excavating a burrow on a sunny slope in my backyard. Once the hole was large enough she inserted her voluptuous rear-end into the burrow, presumably to deposit eggs. After a leisurely and lengthy period, she unplugged herself from the earth and sealed the egg chamber with soil.

After hatching from eggs deposited in the ground, tiny blister beetle larvae called triungulins get busy finding food. In species of Meloe, finding food begins by scaling a nearby blossom to await a visit by a female bee seeking nectar and pollen. When a bee arrives at the flower, the triungulin rears-up and grasps the hairs of the bee with specialized claws on the tips of its tiny legs. The mother bee unwittingly delivers the blister beetle larva back to her brood gallery, where it drops from her body. The triungulin descends into the gallery and consumes the pollen cakes prepared by the mother bee for her young. After the provisions are consumed, the blister beetle larva eats the baby bees – quite tragic really. Triungulins of other species of blister beetles scurry on the ground and locate nests of grasshopper eggs buried in the soil. Hungry triungulans burrow into the soil and the underground omelet becomes a banquet for the blister beetle larvae.  

If you see blister beetles on plants near your home, in the meadow, or feasting on leaves of your potatoes, resist the urge to handle or eat them unless you yearn for a blistering surprise. Stay safe and take a moment to get outside and enjoy bugs.

Acknowledgements 

The delightful treatise “The Bionomics of Blister Beetles of the Genus Meloe and a Classification of the New World Species” by John Pinto and Richard Selander was referenced in preparation for this episode.

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Last week we returned from several weeks of tropical adventures to the DMV and visited delightful ground-nesting plasterer bees. This week let’s meet the tiger king of the insect world, a beautiful tiny terror, the six-spotted green tiger beetle. Recently, I received an inquiry from a neighbor who discovered a stunning emerald green creature entangled in a sheet of plastic covering a backyard water garden. My hopes for capturing a leprechaun and its attendant pot of gold were dashed when the accompanying image revealed a lovely six-spotted green tiger beetle that had somehow become trapped in the translucent plastic jungle. Tiger beetles are well-adapted to hunt. Exceptionally long legs provide lots of ground clearance and enable bursts of speed as they dash across the forest floor. Large eyes enable them to peruse their surroundings for signs of movement and potential meals. Unlike praying mantids that are “sit and wait” predators, tiger beetles actively stalk, pursue, and capture their victims. As I have observed tiger beetles, I’ve found that tossing a small twig in the vicinity of a hunter often triggered an inquisitive charge as the beetle scrambled to see if a potential meal had entered its ambit.

Six-spotted green tiger beetles prowl in a terrarium while keeping an eye out for a meal. It looks like this tiger beetle has no intention of sharing its dinner with a nosy cricket.

Like its feline namesake, the tiger beetle has powerful jaws used to subdue its victim. Each jaw is armed with several stout teeth. The jaws grasp, pierce, and crush. Tiger beetles are carnivores as both adults and juveniles. The female tiger beetle lays her eggs singly on the ground. Upon hatching, the immature stage, the larva, constructs an underground burrow. From this lair, the larva stealthily awaits dinner. As a hapless insect or spider strolls by, the larva springs from the hole like a jack-in-the-box and impales its victim with impressive jaws. The prey is then drawn into the burrow and eaten. Strange hook-like structures found on the abdomen of the tiger beetle larva help anchor it in its burrow. As generalist predators and members of Mother Nature’s hit squad, tiger beetles consume pests in our gardens and landscapes and provide the important ecological service of biological control.

 Tiger beetles are tough to capture without a net, but if you catch one, be careful; they have powerful jaws and can give you a little nip. On a recent trip to the Western Maryland Rail Trail near Hancock, Maryland legions of six-spotted green tiger beetles capered and dodged bicycles and walkers along the asphalt surface. As I slithered on the ground to photograph tigers, one inquisitive hiker shared his observations of the beetles as he encountered them along the sun-dappled trail. He said “When you get too close, those critters fly up and settle down a little way down the path, then they turn around and look at you. When you get close again, they do the same thing.” Good observations.  As I watched the lethal power and speed of tiger beetles, I was glad to be five feet something tall rather than five millimeters in height. This diminutive tiger will be common along sunny bike trails and paths in the forest over the next month or so. A quest for six-spotted green tiger beetles at an appropriate social distance is a tonic on these days of sequestration, and well worth a walk in the forest on a fine spring day.

Sunny bike trails and paths through the forest are great places to watch six-spotted tiger beetles, but alas, fast wheels and speedy feet may spell danger for inattentive tigers.  

 Acknowledgements

 “An Introduction to the Study of Insects” by Borrer, De Long , and Tripplehorn was used as a reference for this Bug of the Week. Thanks to Anne Marie for providing the inspiration for this week’s episode and for releasing her tiger beetle back into the wild.  

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Our recent visits to the rainforests of Costa Rica have been delightful, but spring has finally sprung and I am getting a flood of interesting messages from Bug of the Week viewers discovering cool and creepy insects in and around their homes. This week we bring it back to the DMV to learn about some homegrown critters.

Last summer while teaching in Philadelphia, an avid gardener shared an interesting story about ground nesting bees laying claim to large portions of her yard. She followed up with me in February with a truly amazing picture of her landscape, where literally hundreds if not thousands of ground nesting bees now reside in her yard. Fortunately, before the shelter-at-home orders kicked into high gear, I was able to visit a park and vacant golf course to piece together more details about these fascinating ground-dwelling bees known as plasterer bees. Along with beetles, flies, and butterflies, bees are among the premier pollinators on the planet. Plasterer bees are some of the very first native pollinators to appear each spring. The name plasterer stems from their intriguing behavior of building galleries in the ground and then coating the interior surface of their burrow with a thin, glossy, translucent material produced by a gland in their abdomen. Plasterer bees use their tiny mouthparts to remove the soil while constructing their galleries. The excavation is accompanied by a buzzing sound that may help loosen particles of soil and aid in the digging process. The bee’s mouthparts are also used like a mason’s trowel to spread the glandular secretion on the inside of the burrow before it dries into a cellophane-like coating. How clever! This habit of sealing their galleries gives this bee the common name “plasterer bee”.

What’s up with all these holes in the ground? Watch and learn a little bit about the fascinating lives of delightful plasterer bees.

Plasterer bees are relatives of honeybees and bumblebees but, unlike their cousins, these bees are solitary. Rather than living in a communal nest, each female plasterer bee constructs a subterranean gallery of her own to serve as a home for her brood. Burrows are provisioned with a semi-liquid concoction of nectar and pollen from flowering plants that bloom early in the spring. This yummy delight is food for bee larvae that develop during the summer and fall within the galleries. Although they are not considered social insects, large numbers of plasterer bee galleries are often abundant in close proximity in sandy soils with thin vegetation. Plasterer bees emit a delightful citrus-like odor when handled. This odor is a pheromone produced by a gland in the head of the bee. The pheromone contains linalool and other aromatic compounds that may help plasterer bees find nesting sites, food sources, or potential mates.

While exploring nesting sites along a trail in Rock Creek Park and at the vacant golf course nearby, I was delighted to see dozens of small plasterer bees zooming inches above the ground. While swarming bees at the margin of fairways might dismay some golfers, fear and worry are unwarranted. Unlike yellow jackets, bald-faced hornets, and other stinging terrors, plasterer bees are docile and extremely reluctant to sting. Remember, each female bee is a mother and to risk her life by stinging a human could mean instant curtailment of her reproductive potential should she die in the encounter. Over large areas of a balding zone in the rough, several burrows could be found in each square meter of ground. The plasterer bees were not responsible for the balding turf. They simply colonize areas where the turf is naturally thin. Improving the density of grass will probably reduce the abundance of bees if this is your goal.

If you see swarms of small hairy or metallic colored bees constructing burrows or emerging from galleries in your garden or lawn, please resist the urge to treat them with insecticides. Several species of native pollinators, including anthophorid bees, yellow-faced bees, andrenid bees, halictid bees, and plasterer bees nest in the ground. Enjoy these beauties and give them a break. They pollinate plants and keep our planet humming. 

Acknowledgements

Bug of the Week thanks native bee guru Sam Droege for helping to identify bees seen in this episode. We also thank Marlene for sharing an image of her bee-friendly yard and providing the inspiration for this story. The wonderful article “Ecology, Behavior, Pheromones, Parasites and Management of the Sympatric Vernal Bees Colletes inaequalis, C. thoracicus and C. validus by S. W. T. Batra was used as a reference.

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Cabin fever, dreary weather, and a scary virus; let’s get out of town and take another visit to the magical tropical rainforests of Costa Rica, home of raucous cicadas, fungus farming ants, marauding army ants, and mutualistic ants guarding trees. While hiking along a winding gravel road, I was spellbound by a parade of beautiful Morpho butterflies, fancy fliers who also found the rugged thoroughfare a fine fairway through the rainforest. 

The iridescent burst of blue color, the signature of the blue Morpho, is produced by the physical structure of tiny scales covering its wings. A multitude of thin layers of insect cuticle comprising each scale reflect only certain wavelengths of light to produce the shimmering display of blue as the butterfly dances through the forest. The ‘flash and vanish’ pattern of flight that Morphos display is startling indeed, and likely difficult for would-be predators to track. This form of physical coloration contrasts with other forms of color we see in insects. In many insect species color is produced by storing pigments in their exoskeleton. This mode of color production is employed by critters such as milkweed bugs and Asian multicolored ladybird beetles.

Basking in the sunshine, the blue Morpho is easy to see, but in the wild a clever ‘flash and vanish’ flight pattern makes it difficult for a predator or bug geek to track this gorgeous butterfly.

In addition to this startling display of color, the blue Morpho has evolved another clever strategy for dealing with predators. Intricate patterns of scales on the underside of their hind wings create an illusion of large staring vertebrate eyes complete with pupils and irises. It is thought that these intricate eyespots are used by the butterfly to startle or otherwise confuse hungry predators such as birds or lizards. Studies have shown that the more closely the pattern resembles an eye, the more likely a predator is to be deterred by the ruse. Another theory suggests that the false eyespot may draw the attack of a predator away from a vital body part, such as head or abdomen, to a less vital area such as the end of a wing. How well this works is known for certain only by the butterfly and its predators.

A busy proboscis laps nutrients from rotting fruit, one of the preferred foods for many butterflies including the blue Morpho.

Fermenting fruit is one of the favorite foods of adult Morpho butterflies, but adults can also be found dining on sap fluxes on tree trunks, minerals at mud puddles, and nutrients from dung. Like other members of the butterfly clan, Morpho butterflies possess a long proboscis that uncurls to lap up liquid nutrients. Morpho caterpillars have chewing jaws that remove tissue from the leaves. More than 20 species of Morpho butterflies are found in the new world tropics and their larvae eat a wide variety of host plants ranging from blades of grass to leaves of legumes. Morpho butterflies, one of Mother Nature’s most fascinating creations.

Acknowledgements

Information for this episode came from the wonderful Featured Creature web site “Common name: blue morpho butterfly, scientific name: Morpho peleides Kollar (Lepidoptera: Nymphalidae)” by Haleigh A. Ray and Jacqueline Y. Miller. To learn more about Morpho butterflies, please visit that website. Several images used in this episode were taken at the McGuire Center for Lepidoptera and Biodiversity of the University of Florida. We also thank Costa Rica Vacations, and the intrepid guides Mono and Kenneth at Rafiki Lodge, and Ale and Gera at Playa Cativo Lodge, for providing the inspiration for this episode.

Please stay safe at home as much as possible, but escape every now and then on adventures with Bug of the Week. 

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Over the years, we have visited magical periodical cicadas of Brood II, Brood V, Brood X, Brood XIII, and Brood XIX as they appeared in the eastern half of North America. This week we venture once again some 2,000 miles south to the rainforests of Costa Rica where we previously visited agrarian leaf cutter ants, rapacious army ants, and mutualistic ants protecting Acacia and Cecropia trees. Unlike periodical cicadas that emerge by the millions in prime number years of 13 and 17, several species of cicadas in Costa Rica make their appearances annually. The diversity of Costa Rican cicadas of about 30 species rivals that of eastern North America.

The immature stages of cicadas, called nymphs, spend the majority of their life underground sucking sap from the vascular xylem tissue of roots. Xylem transports water and minerals from the soil to the photosynthetic tissues in the canopy of the plant; however, compared to other plant tissues, xylem is rather low in nutrient content. Bear with me, this is important later. After completing development in their subterranean crypts, a process lasting one to several years depending on the species, nymphs emerge from circular holes in the soil, usually at twilight, and race to vertical structures to climb up and shed their skins. At night tree trunks and other vegetation are festooned with nymphs as they escape their nymphal exoskeletons and emerge as adults. After molting they scramble to the relative safety of the canopy. Once the new exoskeleton hardens, they fly to the treetops to join others of their species in a spectacular throng of cicadas chorusing, courting, mating, and feeding. No social distancing here!

At twilight cicada nymphs emerge from circular escape holes in the soil to scale vegetation and shed their exoskeleton. Next stop will be the treetop to join the chorus and find a mate.

On a recent visit to the rainforest with a group of curious naturalists, we visited a rambunctious swarm of cicadas cavorting in the treetops. Bug of the Week viewers who have witnessed the emergence of periodical cicadas here in the United States will recall the other-worldly sound and volume of a cicada chorus. Their songs can approximate 100 decibels, a noise as loud as a four-cycle lawn mower engine. As we approached a forested ridge near the heart of a cicada chorus, the volume seemed to best that of our periodical cicadas back home. Some of our brave adventurers described the sound of the chorus as “painful”. Witnessing the big boy band in the treetops (only the males sing) was fascinating, but what really sparked my interest was a promise made by our guide who claimed cicadas would be so numerous in the treetops that their “pee” would be like rain. Well, thinking back to John Fogerty’s 1970 lyrical query “I wanna know, have you ever seen the rain, comin’ down on a sunny day”, how could one not resist the chance to experience a cicada shower? Recall that cicada nymphs feed on nutrient poor xylem of plant roots. Cicada adults have sucking mouthparts and they too imbibe xylem fluid, lots of it. Due to the low concentration of nutrients in xylem, cicadas must process vast quantities of sap to gain sufficient nutrients. Their specialized digestive tract enables them to suck copious amounts of sap from the tree and rapidly excrete the excess fluid. Not exactly “pee”, but surely liquid waste. And sure enough, our guide spoke truly. Amidst the cicada chorus in a rainforest on a ridgetop, I did indeed see and feel rain comin’ down on a sunny day.   

High on a ridgetop in a tropical rainforest, cicadas gather to chorus, court, and mate. To sustain these activities, they imbibe large quantities of xylem fluid. Amidst the thunderous din of their serenade, copious excess fluid is excreted and creates a cicada shower. In the cicada-filled rainforest it does indeed rain on a sunny day.

Acknowledgements

We thank Costa Rica Vacations, wildlife enthusiasts Jerri, Parker, Richard, Anita, Maya, and the intrepid guides Mono and Kenneth at Rafiki Lodge and Ale and Gera at Playa Cativo Lodge, for providing the inspiration for this episode.  Huge thanks to cicada sleuth Ale for putting the likely name of Dorisiana cachla on this week’s star. The informative article “Cicada Ecology in a Costa Rican Tropical Rain Forest” by Allen M. Young, and the Cicada Mania Website were used as references for this episode.

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Last week we met fierce Pseudomyrmex ants protecting their tropical myrmecophyte home, the Acacia tree. Myrmecophytes are plants that form a symbiotic relationship with feisty ants which serve as bodyguards. Another group of trees common to tropical forests are Cecropias, a collection of several dozen species many of which are pioneer trees found in disturbed areas along roadways, riverbanks, or light gaps bordering dense tropical forests. Eons ago many species of Cecropia formed partnerships with ants in the genus Azteca. This mutualistic “deal” has two parts. Cecropia trees provide several sources of food including glycogen (a carbohydrate storage molecule), proteins, and lipids in structures called Müllerian bodies, found at the base of a leaf’s petiole, and in Food Bodies scattered on the petioles and blades of young leaves.

Undisturbed, Azteca ants patrol their host at a leisurely pace, but with a shake of a leaf workers swarm from within the stem to defend their colony. I could not resist the chance to assess the potency of Cecropia’s defenders. Compared to last week’s attack by ants guarding Acacia, the sting of Azteca was mild. However, to a caterpillar or beetle attempting to eat leaves of Cecropia, a mass attack by dozens of tiny stinging bodyguards might convince an intruder to seek a meal elsewhere.

Cecropia also satisfies the “gimme shelter” requirement for Azteca ants. The hollow stems of Cecropia are the perfect redoubt to house the queen and raise the brood. And what does Cecropia get from the “deal?” Protection. Clever studies demonstrated that Cecropia devoid of their Azteca bodyguards received more damage from marauding chewing herbivores such as beetles and caterpillars. An additional benefit of ant occupation was the removal of aggressive vines capable of smothering young Cecropia trees. The net effect of ant bodyguards revealed in these studies was more rapid growth in trees protected by tiny but fierce Azteca defenders. For a pioneer species like Cecropia, any advantage you can get on your competitors is an important one and Azteca ant bodyguards may provide just the advantage you need to survive in the wild tropical forest.

On the surface of the trunk, small holes allow Azteca workers to enter an exit the colony. Within the hollow stem, workers tend hundreds of eggs and larvae produced by the queen.

Acknowledgements

We thank Costa Rica Vacations, and the intrepid guides Mono and Kenneth at Rafiki Lodge and Ale and Gera at Playa Cativo Lodge, for providing the inspiration for this episode. The wonderful books “The Insect Societies” by Edward O. Wilson, “The Ants” by Bert Hölldobler and Edward O. Wilson, and the fascinating articles “Azteca protection of Cecropia: ant occupation benefits juvenile trees” by Eugene W. Sehupp and “Food bodies of Cecropia pachystachya (Cecropiaceae) leaves: structural and functional features suggesting complementary role to Müllerian bodies” by Patricia Gonçalves-Souza and Elder Antonio Sousa Paiva, were used as references for this episode.

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