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 digger wasps are solitary wasps; that is, they live independently rather than in social colonies and they do not depend on other members of a colony to share in the raising of young or the maintaining of a nest. There may be several females working independently to nest in a small area and several males may be "swarming" in the vicinity.
Solitary wasps provision underground burrows with paralyzed insects that become food for their offspring. Cicada killer wasps capture annual cicadas and place them in cells located at the ends of the 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. The other two digger wasps provision their nests with grasshoppers.
The female solitary wasps have the capability to sting, but won't unless handled or threatened. Stings inflicted by solitary wasps are usually not severe but reaction varies with the individual person.
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 insecticide dust (e.g., Sevin garden dust) 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.
This article originally appeared in the July 26, 1996 issue, p. 137.