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In the late weeks of summer, Evanstonians may have noticed the unique, small mounds of dirt along some of the spaces between the sidewalks and lawns throughout the City.
They also may have wondered about the large, intimidating wasp-like creatures burrowing underground, creating the mounds of dirt.
“The cicada killer wasp may look threatening, but I have never heard of anyone actually being stung by one,” says Karen Taira, environmental educator at the Evanston Ecology Center.
“There is no reason to be fearful of the cicada killer wasp,” says Stephen Swanson, director of the Grove National Historic Landmark in Glenview. “In fact, they are interesting creatures to study.”
Mr. Swanson has been studying the wasps this summer at Gilson Park in Wilmette where hundreds of cicada killer wasps have burrowed into the sandlot.
Although the wasps do have a stinger, it is used for a single purpose: to paralyze a cicada and feed it to its young.
The female cicada killer wasp, which can measure up to 2″ long, digs burrows each summer in well-drained lawns, sloping terrains and sandy areas, making Evanston an ideal habitat.
After digging her burrow, the cicada killer will then search for an annual cicada, paralyze it with her stinger and take it toward her burrow. This return flight to her burrow is difficult because the cicada is often twice her weight.
After dragging the cicada into the nest cell, she lays an egg on it and seals the cell. She will add nest cells if she needs to off of the main burrow tunnel. A single burrow may eventually have 10 to 20 cells.
The eggs hatch a few days after being laid and the cicadas serve as food. The young wasp then hibernates underground in a hard cocoon and will dig its way to the surface in July or August. The adult cicada killer will live above ground for a mere 2-6 weeks.
“The cicada killer’s life cycle appears to be in synchrony with that of its host,” says Mr. Swanson. Like the annual cicada, the cicada killer spends 90 percent of its life underground.
Ms. Taira says she is not sure why more residents have been noticing the killer cicada wasps in recent years. “It may be due to the hatching of the 17-year cicada last year, but the cicada killer wasps have always been in this area, because they normally go after the annual cicada.”
Mr. Swanson is not certain, but says climate change may be a contributing factor to an increase in cicada killer wasps.
“Bees and wasps are often used as indicators of climate change,” says Mr. Swanson.
Mr. Swanson adds that one may want to think twice before using pesticides to rid your property of the wasps. “Chemicals would only kill this year’s wasps and if your property is attractive to them, cicada killers will likely return next year.”
In the meantime, remember, as the weather gets cooler and the days shorter, all of the summer’s pesky critters will be long gone and there will only be snow blizzards and freezing temperatures to tolerate.