Warning to Cicadas: Watch Out
Eastern cicada killer wasps (Sphecius speciosus), also called giant cicada killers or sand hornets, appear each summer, usually in July, about the same time as their sole larval food source, dog-day or annual cicadas. Despite their large size and seemingly aggressive behavior, they are not dangerous to humans.
These wasps are impressively large; males are about 1 ½ inches long, while females are up to 2 inches in length. A black abdomen with bands of whitish-yellow, orange-red head, eyes, thorax, wings, and legs, and occasional "in-your-face" behavior, combine with their imposing size to create an intimidating presence.
Since the Asian giant hornet appeared in the Pacific Northwest in 2020, the infamous "murder hornet," people may confuse cicada killers with it. Although their size and coloration are somewhat similar, the Asian giant hornet has not been found in North America outside of the Pacific Northwest. The behavior and lifecycle of these two large insects are sufficiently different to avoid any confusion.
Cicada killers are one of many species of solitary wasps. Each female cicada killer wasp constructs her own individual burrow in loose, sandy, dry, or well-drained soil, preferably in an area with little vegetation and full sunlight. If you find many wasps in one area, it is because they have all found the conditions to their liking, not because they are forming a social colony.
Because cicada killers are solitary and do not defend a nest containing a queen and brood, they are unlikely to sting and generally will ignore humans. The wasps focus on finding a mate and then on finding prey to provision their larvae-to-be. If you happen to get in his way, the male wasp may "dive bomb" right in front of your face in defense of his territory, but, lacking an ovipositor, he is unable to sting.
Meanwhile, the female cicada killer wasp excavates a burrow about 1 ½ inches in diameter that may extend 12 to 24 inches in length and up to 12 inches deep, adding side chambers for each larva and its provisions. She shovels out the dirt between her legs as a dog would, creating a large horseshoe-shaped mound at the entrance in the process.
The female wasp then skims over the lawn in search of cicadas. If you happen to be in her way, she may zig-zag in front of you, memorizing your position as a landmark to find her way back to the burrow after the hunt. Once she has captured a cicada, she paralyzes it with her stinger and then holds its lengthwise under her body, as she glides or drags it back to the nest. The cicada’s weight can be a cumbersome burden for the female to carry at times. Once in the burrow, she will lay an egg on the paralyzed cicada and then stash it in a larval chamber and head out again for more. When the egg hatches, the larva burrows inside the paralyzed cicada to feed on it, then overwinters as a mature larva inside a cocoon until pupation the following summer.
There is only one generation per year, and the adult wasps live for only about two to three months, from July to September, feeding on plant sap and flower nectar. As much as possible, ignore them during this time if you can; they have no desire to tangle with you. Take this opportunity to educate family and friends about these amazing and beneficial insects that share our landscapes.
Generally, it is not necessary to take steps to get rid of them. However, if they become a nuisance by nesting in an area with a lot of human activity, such as a deck, patio, or pool area, you may want to do something to manage them. If there are only a few, you can take aim with a tennis racket to knock them down. For a few nests in a small area, a piece of clear plastic tarp laid over the ground and secured may discourage the wasps from staying. If possible, provide an alternative area with similar soil and site conditions but out of range of human activity where the wasps can burrow undisturbed.
If the wasps are too numerous to ignore, you may need to resort to insecticides. Dust formulations of a labeled insecticide, such as a synthetic pyrethroid, are the most effective. Sprinkle the dust into the burrow opening, in late evening or early morning, when the wasps are relatively inactive. Apply it early enough in the season to catch the female while she is still provisioning the nest. The wasp picks up the insecticide on her feet as she moves in and out of the burrow; you should not disturb or fill in the opening. For any pesticide, read and follow the application directions carefully.
