I have found some holes dug between the bricks in my driveway. There are little piles of sand by the holes, and I was wondering what insect might be making them; I do not see any ants in the vicinity. There have been some unusually large wasps flying
around this area.
— Jeffery Pearl, Highland Park
Your description sounds like there may be cicada killer wasps nesting in your driveway. I have them in my driveway at home and enjoy watching them. They can be considered a beneficial insect that helps control annual 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. When you see these large insects in the garden, they can seem very intimidating. A male cicada killer wasp may fly up to you to investigate when 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. This insect is no cause for concern in your garden. If you’re lucky, you may see one bring in an insect to place in the burrow to lay eggs on.
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 a ½-inch wide in the ground. You’re seeing the entrance holes and the typical soil pile surrounding 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 egg hatches into a legless larva that consumes the paralyzed insect. 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, then use mulch, plant groundcovers 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. You can also use irrigation to deter nesting. 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.
