Month: July 2021

Several weeks ago, on June 21, Bug of the Week said farewell to Brood X periodical cicadas in the DMV. However, this week there is one more tale to tell about these iconic invertebrates. As interest in Brood X developed this spring, one of the most frequently asked questions was “how many cicadas will there be?” Although it was and is impossible to answer this question precisely, estimates of billions were often bantered about and those prone to hyperbole guesstimated numbers in the trillions. If that sounds like a lot of cicadas, ruminate on this for a moment. Recall that female cicadas lay eggs in the treetops and upon hatching, cicada nymphs tumble to earth and enter the soil to feed on tree roots. It is widely reported that each female cicada has the potential to lay from 400 to 600 eggs during the course of her lifetime. Suppose that only 10 billion female cicadas lived to reproduce fully and each laid a modest 400 eggs. This would translate into a several trillion cicada nymphs falling from trees in the eastern half of the United States courtesy of Brood X. Yikes!

This week an eminent member of the press corps inquired about potential showers of cicadas raining down on citizens in the DMV as billions of cicada nymphs hatched from eggs imbedded in small branches and tumbled to the earth below. The ancillary question was, of course, would people notice the cicada shower? Recalling a recent dewy shower of cicada pee while studying cicada behavior, I anticipated a repeat performance while working under trees wearing scores of flagging branches and hundreds of healthy branches bearing thousands of cicada egg nests. To date I have not experienced a deluge of cicada nymphs dropping from trees, despite the fact that egg-hatch is in full swing as of this writing.

During most of their embryonic development, little detail can be seen of the cicada nymph within the egg. Within days of hatching however, eyes become visible in hues of red or brown. Using muscular contractions, cicada nymphs slither from the confines of their eggshell, ready to skedaddle in a matter of minutes. After tumbling from the treetop to earth, they join thousands of brood mates entering the soil in search of plant roots that will sustain them for the next 17 years.

Part of the explanation why I and most other people will not notice periodical cicadas as they hatch and fall to earth is the minute size of cicada nymphs. At only a couple millimeters in length they are very hard to spot. Their small body mass may allow breezes to carry them beyond the dripline of trees from which they hatched. Although siblings from a single egg nest hatch somewhat synchronously, each cicada takes a few minutes to escape from an egg, thus causing hatching to be dispersed in time. Remember too that egg laying was distributed over several weeks in May and June. This further spreads out the rainfall of hatchlings in time. As evidenced by the massive numbers of trees with flagging branches, whether or not you encounter a shower of cicadas falling from trees, rest assured that barring some unforeseen catastrophe Brood X will return in force in 2038 here in the DMV. 

Acknowledgements

Bug of the Week thanks Paula Shrewsbury for contributing images and commentary for this week’s episode. We thank the writers of the Washington Post for providing inspiration for this episode and for their enthusiastic, continuing in-depth coverage of Brood X. Much of the background information for this episode and others was taken from “The ecology, behavior and evolution of periodical cicadas” by K. S. Williams and C. Simon, and references therein.

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The DMV abounds with some of the best nature centers in the country. Two of my favorites are Woodend Sanctuary, nestled inside the Beltway in Chevy Chase, Maryland and home of the Audubon Naturalist Society, and the Howard Conservancy, a 232-acre wildlife sanctuary in Woodstock, Maryland. Summer is always an exciting time to take a suburban safari at these refuges when some of Mother Nature’s wildest flowers are at their best. On a recent trip to the Howard Conservancy, large patches of Heliopsis, a.k.a. false sunflower and oxeye, were in dazzling full bloom. Oxeyes are full bodied members of the aster clan and our native species are dynamite attractors for many interesting insects.

While immersed among some oxeyes, I was surprised to find hordes of gorgeous seed bugs busily sucking nutrients from the developing flowers and engaging in their buggy mating rituals amongst the blooms. These little beauties are close relatives of other true bugs like the milkweed bugs and scentless plant bugs we’ve met in previous episodes. In fact, early records often confused this species with small milkweed bugs and recorded it as a denizen of milkweed. Careful observations by one Reverend James M. Sullivan of St. Louis, Missouri, helped clarify the true pattern of food choice of false milkweed bugs. However, the name false milkweed bug is a bit of a misnomer, as these little rascals actually are connoisseurs of members of the aster family.

Heliopsis is a great plant to spot false milkweed bugs. Watch as the bug on the left nonchalantly grooms its antennae while its mate taps its left hind leg somewhat impatiently while dining on a floret. Bugs are pretty entertaining.

After choosing a handsome mate and consummating the relationship, the female false milkweed bug lays eggs in batches of 15 to 50. Eggs hatch and bright red nymphs use their elongated sucking mouthparts to sip fluids from the plant. Adults can live two months, and along with their nymphs these beauties can be seen on oxeye from June through August in many parts of the country. Bug of the Week recommends a trip to the meadows and gardens at Woodend Sanctuary and the Howard Conservancy to glimpse members of the aster clan. If you encounter glorious oxeyes, take a few moments to hunt for false milkweed bugs.

Acknowledgements

We thank Woodend Sanctuary and Howard Conservancy for providing inspiration for this episode. The interesting article, “On the Biology and Food Plants of Lygaeus turcicus (Fabr.) (Hemiptera: Lygaeidae)“ by James A. Slater, was used to prepare this episode.

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Homonyms, words with two or more meanings, are interesting constructs of any language. For example, take bark, it has a couple meanings. It can be the corky tissue protecting the outside of a tree or the vocalizations of furry, four-legged mammals that like trees for, well, you know. My dictionary defines squash as a noun meaning “vegetable of the gourd family” and as a verb meaning “to crush something with pressure.” Let’s look at the first meaning of squash. Squash, zucchini, pumpkins, and gourds are all delectable and nutritious members of the cucurbit family. However, humans are not the only ones that find these prickly plants scrumptious. In a previous episode of Bug of the Week, we met the dastardly squash vine borer, a caterpillar with the power to wilt even the toughest pumpkin vine. While admiring some squash vines in a community garden, I noticed several plants with wilted, yellow leaves. A closer inspection failed to find bad borers, however, the leaves of the squash were loaded with immature and adult squash bugs merrily sipping sap.

Squash bugs are members of the true bug clan, meaning they have an elongated beak for sucking liquid food, wings that are part membranous and part leathery, and, as juveniles, they are known as nymphs. We met other members of this cantankerous clique including bed bugs, brown marmorated stink bug, boxelder bug, and wheel bug in stories past. Both nymph and adult squash bugs consume fluids from their cucurbit hosts and problems arise when dozens of feeding squash bugs jab so many beaks into the vascular system of the plant. Inserting the beak damages the plant’s vascular system. In addition, squash bugs can transmit a nasty bacterium, Serratia marcescens, causing what is known as cucurbit yellow vine disease. These insults and removal of vascular liquids cause plants to wilt. When squash bugs are abundant, their damage can reduce the bounty produced by your squash and zucchini vines.

Who doesn’t love pattypan squash? But look out pattypan, those clusters of bronze eggs will soon hatch into tiny green and black squash bug nymphs. As they grow and molt, white wax cloaks their bodies. If you see adults roaming on your cucurbits, or discover eggs and nymphs, snatch them off and dispose of them in whatever way you like.

Fortunately, there are a few tricks you can use to foil the squash bug’s shenanigans:

1)       At the end of the year, rid your garden of decaying vegetation and remnants of vines and leaves. These refuges are used by adult squash bugs to survive the wild winter.

2)       In spring, plant varieties such as Butternut, Royal Acorn, or Sweet Cheese that are more resistant to squash bugs.

3)       I have spoken to gardeners who place floating row covers over their plants early in the season to help keep these buggers from colonizing their plants. If you go this route, remember to remove row covers when blossoms first appear. If you don’t, then pollinators cannot do their job. No pollination means no pumpkins, squash, or zucchini.

Been waiting for the second meaning of squash? If you see squash bugs, squash the squash bugs. Really, if you have just a few plants, it is relatively easy to inspect plants and when you find the golden-bronze eggs, green or whitish nymphs, or tawny adults, crush them.

If squashing squash bugs isn’t your thing, remove them from the plant and drop them into a vessel of soapy water. Squash bugs are poor swimmers and when they have expired their tiny bodies can be placed in the compost heap to nourish your garden next season. Have a squashing good time!  

Acknowledgements

Bug of the Week thanks community gardeners of Montgomery and Howard Counties for providing the inspiration for this episode and the backdrops for observing squash bugs.

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Echinacea, a.k.a. cone flower, renowned for its medicinal qualities as well as its beauty, is blooming at full throttle this week in gardens here in the DMV. Just after sunrise, the fragrance of cone flowers is delightful not only to humans, but also to a raft of pollinators. Bumble bees are usually the first arrivals in the morning, but shortly thereafter industrious bees, members of the halictid clan, arrive to collect nectar and pollen for youngsters in their colonies. The name “sweat bee” is a little goofy and somewhat misleading. These bees don’t sweat, but like sweat bees we visited at Bug of the Week some years ago, some halictids alight on humans and imbibe salt-rich perspiration. Guess this is why they are called sweat bees.

Unlike mason bees and plasterer bees we met in previous episodes, which are solitary with every female caring for her own young, halictid bees vary in their social structure. Some species like Agapostemon virescens adopt the solitary life style, while others like Halictus ligatus are eusocial (truly social) with queens producing non-reproductive daughters known as worker bees, tasked with foraging for nectar and pollen and tending the brood of their mothers. Colonies are founded in spring by females, survivors of winter’s ravages. The sweat bees we’re visiting this week adore cone flowers as a source of food, and both build nests in soil. Founding queens of Halictus ligatus gather pollen and lay eggs that hatch into daughters, worker bees, destined to help with caring for the young and gathering food for the colony. Some of these daughters will eventually become reproductively active and produce daughters and sons of their own. A fascinating study of Halictus ligatus by Miriam H. Richards and Laurence Packer discovered that when weather conditions were favorable, worker bees survived at greater rates and grew larger. Some of these large workers produced their own offspring. However, under less favorable conditions of temperature and food availability, workers were smaller and produced fewer offspring of their own, submitting to larger, more aggressive queens that produced the majority of offspring. Shifting conditions of temperature and food availability govern the social dynamics of halictid bees like Halitcus ligatus.

Cone flowers are a gold mine for many kinds of pollinators. Watch as female halictid bees, a.k.a. sweat bees, gather and store huge loads of pollen in pollen baskets, called corbiculae, on their hind legs. The smaller bee in the first two clips is Halictus ligatus or its sibling species, Halictus poeyi, and the last clip is the gorgeous Agapostemon virescens.  

Beautiful Agapostemon virescens, sometimes called “little green bees”, favor loamy soils with sparse vegetation as prime real estate to build their nests. Individual nests may contain more than 100 brood cells and, while more than one female has been observed in a single nest, this species is considered to be solitary. Once they find favorable plots of land, many Agapostemon virescens queens may move in and form large aggregations of nests. To enjoy these delightful native pollinators, consider letting part of your lush lawn go a little thin in a sunny spot to provide nest sites for nurseries of these bees. Both species of sweat bees and many others of their clan are generalist pollinators and a diversity of flowering plants provide food. However, on this week of Independence Day celebrations, Echinacea and other members of the Asteraceae are dynamite attractors of these beauties to your garden.  

Acknowledgements

Bug of the Week thanks Dr. Paula Shrewsbury for planting cone flowers that served as the backdrop for these delightful bees. Great references consulted for this episode include “Bees of Northwestern America: Agapostemon (Hymenoptera:Halictidae)” by  Radclyffe B. Roberts, “The Socioecology of Body Size Variation in the Primitively Eusocial Sweat Bee, Halictus ligatus (Hymenoptera: Halictidae)” by Miriam H. Richards and Laurence Packer, “The Insect Societies” by Edward O. Wilson, “The bees of the world” by Charles D. Michener, and “Bees, wasps, and ants” by Eric Grissell.  Special thanks to Sam Droege for identifying the halictids featured in this episode.      

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