The eastern cicada-killer wasp may be the scariest-looking wasp in our state. But it is not aggressive to people and is virtually harmless, unless handled roughly. It is an exceptionally large species, with rusty clear wings and the black and yellow markings common of wasps. In addition to their size and coloration, their behavior identifies them.
Males typically defend territories by simply flying around the nests of one of more females. The males' energetic hovering can be intimidating. Male cicada killers may clash with other insects, crashing into them bodily, but with people they usually just fly around and inspect us.
Females also cruise around, looking for good places to dig tunnels and searching around trees and shrubs for cicadas.
Males have a pointy projection on their abdomen tip that amounts to a false stinger, and they may poke it against their enemies in defense, but they are completely incapable of stinging. Females (unless molested) reserve their powerful sting for the cicadas they hunt.
Similar species: Another common Missouri wasp, the eastern stizus (Stizus brevipennis), looks almost exactly like an eastern cicada-killer wasp. But look closely at the yellow markings: in the eastern stizus, the yellow abdominal marks are smooth-edged, while on the cicada-killer, ornate black hook-shaped edges intrude into the yellow. Also, the color patterns on two of the thorax segments are different: in the eastern stizus, the scutellum and postscutellum plates have a distinct pattern of yellow marks, while those plates on the cicada-killer have a plainer, rust-colored patch.
Length: can exceed 1½ inches.
Habitat and Conservation
Female cicada-killers dig nest tunnels in open areas such as lawns and pastures, usually in aggregations. Loose, workable soils are preferred. A mound of excavated soil at the tunnel entrance is often conspicuous. These mounds often have a shallow furrow leading to the tunnel entrance, as if a person had made the furrow by dragging a thumb across the soil.
As adults, female cicada-killers may live for a month and produce tunnels four or more feet long in a single nest. Although nests are not particularly deep, nine or ten cells per nest is not unusual.
To provide food for the young, female eastern cicada-killer wasps hunt annual (dog day) cicadas (Neotibicen spp.), using their stings to paralyze them, then stock their nests with one or two cicadas per cell. Cicada-killer larvae feed on the cicadas.
Adult cicada-killers feed on nectar and other sweet plant juices.
Not harmful to humans. Only the females possess stingers, and they reserve these for use in subduing prey (cicadas). It is possible that a female eastern cicada-killer wasp could sting a person, but only if she is handled roughly. Persons allergic to wasp stings should stay away from all wasps.
Males can seem threatening as they jealously patrol their territories, chasing away other males and even other kinds of insects that flutter into the area. But they lack stings entirely and are completely harmless.
Males usually emerge before females and begin establishing territories about the same time dog-day cicadas emerge and start singing, in midsummer. Females emerge and dig nest tunnels; then they hunt, sting, and paralyze cicadas, transport them to the nest, drag them inside, and lay an egg on them. The larvae hatch in a few days and start eating the cicadas. Within a month, they finish growing, form a protective cocoon, and overwinter. In spring they pupate for about a month, then emerge as adults.
Sometimes the tunneling of this species disfigures lawns; the flip side is that it aerates the soil and helps rainwater to soak in. This species also provides us with drama: A mama cicada-killer gliding with, then dragging, a huge, immobilized cicada to her nest is truly an impressive spectacle.
Although they prey on cicadas, cicada-killer wasps are themselves preyed upon by a group of wasps called velvet ants. The female velvet ant sneaks into the cicada-killer’s tunnel and lays an egg in a nest cell. The cicada-killer larva eats its cicada and grows; when it pupates, the velvet ant larva eats the pupa.
Behaviorally, there's usually a big difference between social bees and wasps and solitary ones. For example, social wasps, such as yellowjackets, are quite willing to sacrifice themselves to attack intruders if they feel their communal nest (including all their sisters, eggs, and young) is endangered. But a solitary wasp, like the cicada-killer, has little incentive to endanger herself in such attacks, because if she dies in the attempt, there are no sisters to keep her nest going.