Month: April 2020

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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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