July 13, 2017 

Mid-Summer Visitor

            I was going to talk about something else today, but I had the first of what is a series of calls I get each summer about a large intimidating wasp that was digging holes in this lady’s flowerbed. Her description was perfect as she described their appearance and the size of holes they were digging. Her concern was each day there seemed to be another one... when I talked to her, she was up to three.

            She wondered what they were and what she should be doing about them. I could hear her sigh of relief several miles away when I assured her that no control measures were necessary and if she didn’t bother them, it was very unlikely they would bother her. These large wasps are our perennial mid-summer visitor, the cicada killer.

            Each year, people will bring large wasps in a variety of containers to the Extension office while the less daring just describe what they see around their homes. The description usually goes something like this... "It's a large yellow and black wasp that kept buzzing around the same place in the lawn." or "It's a huge hornet that keeps coming back and won't go away." or my favorite, "It's the biggest wasp I've ever seen and it scares the bejeebers out of me."

            These are all fairly accurate descriptions of the cicada killer. These large black and yellow wasps, up to two inch long, tunnel in disturbed areas, creating soil mounds and cause concern about stings. In spite of their menacing appearance and seemingly aggressive behavior, these wasps only rarely, if ever, sting. As one insect expert described them, they are a wimp in the wasp world. They are not a threat unless stepped on with bare feet or a person tries to hold one in their hands.

            These wasps dig a tunnel in the soil about a half inch in diameter. They get their name, cicada killers, by the next unusual step in their life cycle. After digging a tunnel, they find a cicada and sting it which paralyzes the cicada, but does not kill it. Then they drag this cicada into their tunnel and lay an egg on it. When the egg hatches, the cicada provides food for the larva. It will eventually form a pupa and then the adult wasp hatches out next summer.

            These soil-nesting insects hone in on what are, to them, major landmarks... a stick or a small stone... and use these to locate their nest. When someone moves into the area, suddenly the landmarks seem different, so the wasps dart around, reassessing their position. The wasps are not aggressive, but they can give that appearance. In spite of their intimidating behavior, these wasps can and should be ignored.

            Although the cicada killers are not a problem, there are other insects that do deserve our attention. These include crickets, boxelder bugs, Asian lady beetles and other insects that intentionally or accidentally get into our homes. I’m just starting to see crickets now and later this summer the others will be looking for sheltered places to spend the winter.

            This is a good time to spray around the foundation to form a barrier to control them before they get into your home. Time your spraying (early morning or late evening is best) so it minimizes the effect on beneficial insects that might be around your home or in your landscape plantings. Also, be sure to seal up any cracks or crevices in the foundation or around doors or windows where they might actually get it. A little prevention now will go a long way to preventing problems later.

            For more information about insects in and around your home, contact your local Nebraska Extension office.