Were you one of the lucky (sic) Crozet residents who was visited this summer by large, fierce-looking striped wasps who build nest mounds in the dirt and dive bomb intruders? Then join the club—they’ve been around for years but seem to have become more plentiful recently. Many local residents reported encounters with these cicada killer wasps in Old Trail, Yancey Mills, Westhall, and Broad Axe to the east. One Old Trail resident had about 60-70 holes pop up in her side yard in a week. And an Old Trail Community Garden user had to change her garden plot after she tried to pull up weeds and encountered several of them flying around their in-ground nest. “This gardener is allergic to bees and promptly asked for another plot,” reported Community Garden coordinator Beverly Thierwechter. “But no harm done, no stings!” These non-aggressive pollinators are actually more of an annoyance than a threat.
The eastern cicada killer wasp sphecius speciosus, also known as the cicada hawk or ground digger wasp, can be from ½ to 2 inches long, which makes it one of the largest wasps in the Eastern U.S. (other related species occur west of the Rockies). It has a red body, black and yellow striped abdomen, and yellowish brown wings, resembling an oversized yellow jacket. Adults emerge in summer (late June or early July) and die off in mid-September. These wasps build large, mounded burrows in the ground, usually in dry, barren soil near trees harboring cicadas. They may dig along sidewalk or patio edges, in flower beds, gardens, or lawns. The females then prey on cicadas to provision their nests with fresh food for their future offspring. Eastern cicada killers are sometimes mistaken for European hornets (Vespa crabro), which build paper-like nests and can deliver a painful sting.
But “cicada killer” is a somewhat misleading name. The adult wasps don’t actually kill the cicadas—they paralyze them so their offspring can later eat them alive! Of course, the cicadas do indeed die eventually. After digging the nest, the female wasp paralyzes a cicada with her venomous sting. Holding it upside down beneath her, she flies to her burrow carrying a load that may be more than twice her weight. She will often drag her prey up the nearest tree or fence post to gain altitude for this flight. After placing one or more incapacitated cicadas in the nest, she deposits an egg on each and closes the cells with dirt. Once the egg hatches a few days later, the white, legless larva begins to eat the cicada, while taking care to keep it alive. In about two weeks, it creates an earth-coated cocoon and overwinters in the nest cell until spring, when it emerges as an adult wasp. This means that if you’ve seen them this summer, they will probably be back next year!
Unlike hornets and yellow jackets, cicada killers are solitary wasps. As ferocious as they may appear, they are not aggressive. The female wasp stings only if grasped roughly or stepped on; it will not go out of its way to harm you. The smaller male has no stinger at all! He is territorial, however, and may dive-bomb other insects or people who get too close to the nest. Various methods have been used to try and eliminate these annoying visitors, including pouring boiling water, ammonia, or boric acid into the nest—or pouring in gasoline and lighting it on fire—then blocking the entrance. This procedure must be done at night when the wasps are in residence, or they will simply build again. However, one resident was told by a pest control representative that the only way to eliminate them is to dig up your yard to the depth of about a foot—and they may return in future years, anyway.
So why bother? I hope you’ll think twice before trying to eradicate these harmless insects. Cicada killer wasps are only here for a short time—maybe two months—each summer. They are beneficial both because they are pollinators that feed on flowers, and because they provide a natural control on cicada populations, which protects the deciduous trees upon which cicadas feed. Perhaps they, like the bears, have had their previous habitats eliminated by the rampant building in and around Crozet. As Temple Grandin pointed out, “Nature is cruel, but we don’t have to be.”