At least 3 different species of wasps construct nests in the ground in Iowa. These "digger wasps" include the cicada killer wasp, the largest wasp found in Iowa. Cicada killer wasps may be up to 2 inches long. They are black with yellow markings on the thorax and abdomen and they have rusty colored wings. The great golden digger wasp is slightly smaller. The abdomen is reddish-orange except at the tip which is black. A third species is 1 inch long and completely black with iridescent blue wings.
The cicada killer wasp and other digger wasps are solitary wasps; that is, they live independently rather than in colonies and do not depend on other members of a colony to share in the raising of young or the maintaining of a nest. Other solitary wasps include the mud daubers and potter wasps. Solitary wasps put paralyzed insects or spiders inside the nest as food for their offspring.
Female cicada killer wasps capture annual cicadas in July and August and place them in cells located at the ends of tunnels they have dug in the ground. Each tunnel is about the size of a quarter and extends 24 inches or more into the ground. One or two paralyzed cicadas are placed in each cell, and a single egg deposited before the cell is closed by the female, who flies away, never to return. The wasp grubs feed on the cicadas and develop into wasps that emerge the following summer.
The cicada killer, like other solitary wasps, has the capability to sting, but won't unless handled or threatened. Only female wasps have the ability to sting. Stings inflicted by solitary wasps are usually not severe but reaction varies with each individual.
Wasps are generally beneficial and a nest in an out of the way location where it is not likely to be disturbed should be left alone. If, however, a nest is located where problems could arise, such as under a deck or near an often used door, removal is justified. Ground nests of cicada killers and other digger wasps can be destroyed by placing an outdoor use insecticide dust containing carbaryl in and around the nest entrance during the night. The dust particles will adhere to the wasps as they come and go from the nest. Cover the nest opening with a shovelful of soil after all activity has stopped. For more information on insecticides please see "Insecticides in the Home Landscape and Garden. "