Holes in the ground could be sign of cicada killer wasps — but that’s not necessarily a bad thing
“I have found some large holes in between the bricks in my patio, along with some little piles of sand by the holes. I am not seeing any ants and wonder if I should apply some control measures? I have also seen some large wasps flying around this area.”
— Sonya Hopkins, Niles
Your description sounds like there may be cicada killer wasps nesting in your patio. They are also nesting in my driveway at home like they did last year, and they occasionally buzz around me as I exit my truck.
I like seeing them there. They can be considered a beneficial insect in helping to control cicadas and katydids. Cicada killers are large, about 2 inches long and black to red, with yellow banded markings on the abdomen. The head and transparent wings are reddish brown. Their large size makes them seem very intimidating when seen in the garden.
This insect is no cause for concern; thus, nothing to worry about for your garden. Whenever possible, it is best to simply leave them alone.
A male cicada killer wasp may fly up to you to investigate as you enter his territory, but is unable to sting. The females are capable of stinging, but lack the instinct to guard their nest like a honeybee. You may get stung if you accidentally step on one with bare feet or grab one with your bare hands.
Cicada killers are solitary wasps. This wasp gets its common name from hunting cicadas to supply its young with a food source. The female digs a 6- to 10-inch-deep burrow that is ½ inch wide in the ground. You are seeing the entrance holes and the typical pile of soil that surrounds it in your patio.
The female locates and stings a large insect such as a cicada or katydid and then brings it back to the burrow. She places the insect into a chamber and lays an egg on it; sometimes she puts two in a burrow but lays an egg on only one. She then covers the burrow, digs another, and repeats the process. The egg hatches into a legless larva that consumes the paralyzed insect(s).
Full-grown larvae overwinter in the burrow, pupate in the spring, and emerge as an adult during the summer, usually in July and August. It is unlikely that there will be any impact on the stability of the brick paving in your patio.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.
