Mild mannered female cicada killer wasps are active across Kentucky during the summer, intent on their tasks of 1) digging underground burrows and 2) provisioning them with paralyzed cicadas that will be food for their grub-like larvae. The wasps will be very focused on these tasks for several weeks.
Why are cicada killers so abundant in some areas? These solitary wasps choose sites with specific characteristics: well-drained, light-textured soils in full sunlight that are near trees harboring cicadas. They may dig along sidewalk or patio edges, in flower beds, gardens, or lawns. As much as 100 cubic inches of soil may be brought to the surface as tunnels are formed. This can be unsightly in highly managed turf and the accumulations may smother grass. Sometimes skunks may dig up areas that have been extensively tunneled by the wasps to feed on cicadas and wasp larvae.
Large aggregations of cicada killers can build up over time. An estimated 40% of the developing larvae (a dozen or more per tunnel) may emerge as adults the following year so numbers can increase rapidly.
Are cicada killers dangerous? Females have significant stingers which they plunge into cicadas to inject venom that paralyzes them. Without doubt, their stings are painful. However, they are not aggressive and do not have nest-guarding instinct of honey bees and hornets. You can walk through areas where they are active without attracting attention.
The buzzing noise that the wasps make and the warning colors on their wings and bodies intimidate and discourage predators that see them as a large meal. When attacked, females will use their stinger to protect themselves.
Males lack stingers but are territorial. They will approach anything that enters “their area”, including walkers, people mowing or using weed-eaters, or riding tractors. They may hover and challenge trespassers but are harmless. That can be easy to forget when staring down a big wasp.