Timothy Gibb, Department of Entomology, Purdue University
A number of bees and wasps make their nests in the ground and often around areas where people live and play. The sight of a wasp often evokes fear and anxiety because of their reputation of stinging people.
However, not all wasps are created equal. Many wasps rarely ever sting people. Cicada killer wasps are one of those. They are large, ominous and quite common at this time of year, but are relative wimps when it comes to stinging people.
Education is the single best strategy to help people deal with cicada killers. Understanding their behavior and biology will help to dissipate unfounded fears and concerns.
Most cicada killer wasps that are encountered are males, patrolling the nesting area. They may fly about, dive bomb, or even hover in front of people, but they cannot sting. Male wasps lack a stinging mechanism.
Even female cicada killers are relatively harmless and will sting only if handled. They are often mistaken for social wasps, particularly due to the fact that they nest in aggregations that may consist of a few to several hundred burrows. However, the cicada killer is a solitary wasp, not a social wasp, which means that it is not associated with a large nest or a queen; in fact, typically there is only one individual in each nest or burrow.
Female cicada killers dig burrows in well-drained, light textured soil, typically in an area with full sunlight. The 1½ inch diameter opening leads into an oblique tunnel that runs for 12-18 inches and reaches a depth of 6-10 inches. The female completes and stocks up to four cells, each containing from one to three paralyzed cicadas on which wasp eggs are laid. When eggs hatch the larvae bore into and feed on the cicada.
The larvae overwinter in their burrows, emerging the next summer as adults. Between late July and mid August, these new adults emerge, mate and the female digs new soil burrows, stocks them with cicadas, and the cycle is repeated. Adults die by mid September. A large nesting aggregation results in unsightly mounds of soil that are characteristic of cicada killer activity.
Cicada killers are beneficial wasps and should only be destroyed if they burrow close to where people are. Control of cicada killer wasps is safely and most effectively done by placing a small amount of insecticide dust down into the tunnel opening. Pyrethroid is the most common active ingredient used for these wasps. For a large nesting aggregation, the area can be sprayed using liquid insecticides. In both cases, the tunnel entrances should be left open.