Archive for Thursday, August 9, 2007

Grandchildren’s fears about killer wasps unfounded

August 9, 2007


My two grandsons both ran into the house, telling me of these flying torpedo things on the front stoop (their grandmother was in the lead). The low-flying insects were wasps, and in particular, cicada killer wasps. My explanation to the boys centered on what the wasps were doing and why they were harmless. That deterred the 6-year-old - he just took a wide berth - but the 3-year-old just wanted to catch one (grandmother just left). Harmless to humans in general, they may not be a happy specimen if captured.

Control is usually not required. The cicada killer wasps are generally harmless and naturally helpful. Young children and people who just don't like bugs (grandmother) may see this differently. I treated the burrows after dark to ensure the female wasps were in their nests. Using small amounts of carbaryl (Sevin) or diazinon according to the manufacturer's recommendation is effective. Males can be captured with an insect net or knocked out of the air with a tennis racket during the day.

These cicada killer wasps are attracted by their food source and incubation host, the cicada. Hot and dry summers bring the cicada, and so their predators. Last year I wrote of these wasps, and this year there seem to be more sightings and more questions about them. I repeat that information here as a reminder:

l These cicada killer wasps are 1 1/4 to 1 5/8 inches long, the largest wasp in North America. Large and scary to see, they usually ignore people. If startled or stepped on, the female can sting while the male cannot. Even then, the sting is less painful than that of smaller wasps like the yellow jacket or paper wasp. Recognized by their size, they have a black body with yellow bands across the thorax and abdomen, with reddish-orange wings. They fly 6-10 inches off the ground.

l A wooded area with soft, sandy soil is a favorite habitat. This wasp is solitary, with each female taking care of its own. It is not uncommon to find groups of these insects, three to five pair in one area. The female nests in burrows in the ground. These burrows are quarter-size in diameter and can go 6 inches down and 6 inches horizontally. The male lives on low branches or other foliage. Adults normally live 60 to 75 days from mid-July to mid-September. The adults feed on flower nectar and sap exudates.

Seeming to do all the child-rearing, the adult female also hunts. She stings her prey on lower tree branches and then carries or flies the prey back to her burrow. Here it becomes food for the wasp larva. She will lay one egg per cicada and then stuff them into her burrow. Each burrow normally has three to four cells with one to two cicadas each. However, it is possible for one burrow to have 10 to 20 cells. Eggs hatch in two to three days and begin to feed on the paralyzed cicadas. Feeding continues for four to 10 days until only the outer shell of the cicada remains. The larva overwinters inside a silken case it has spun. Pupation occurs in the spring. There is one generation per year.

Harmless unless trapped or stepped on, they easily can be left alone and soon will be gone. They are a part of nature and not an insect to be feared.

- Stan Ring is the horticulture program assistant at K-State Research and Extension-Douglas County. He can be reached at 843-7058 or <a href=""></a>.


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