“I found some large holes in between the bricks in my driveway, along with some little piles of sand by the holes. I was wondering what insect might be making them, as I do not see any ants in the vicinity. There have been some unusually large wasps flying around this area.”
— Leticia Burns, Evanston
Your description sounds like there may be cicada killer wasps nesting in your driveway. They can be considered beneficial insects 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.
A male cicada killer wasp may fly up to you to investigate as you enter its territory, but it is unable to sting. The females are capable of stinging, but lack the instinct to guard their nests like a honeybee does.
You may get stung if you accidentally step on one with bare feet or grab one with your bare hands. Otherwise, this insect is no cause for concern, and thus nothing to worry about for your garden.
Cicada killers are solitary wasps. This wasp gets its name from hunting cicadas to supply its young with a food source. The female digs a 6- to 10-inch-deep burrow that is 1/2-inch wide in the ground. You are seeing the entrance holes and the typical pile of soil that surrounds it in your driveway.
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 eggs hatch into legless larvae that consume the paralyzed insects. Full-grown larvae overwinter in the burrow, pupate in the spring, and emerge as adults during the summer, usually in July and August.
You will tend to find cicada killers in areas with bare soil or sand like in a sandbox or below playground equipment. If this insect truly is a nuisance for you, use mulch, plant ground covers or install sod to cover bare soil areas.
Sandboxes can be covered with a tarp when not in use, and rake sand under playground equipment to help deter the wasp. Consider using mulch instead of sand in play areas. Irrigation can also be used to deter nesting. But whenever possible, it is best to just leave them alone.
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.
