If you feel a 2-inch wasp with reddish, transparent wings bumping its head against your body this summer, it might be a killer.
Luckily -- unless you're a cicada -- there is not much to fear.
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Cicada killer wasps are back this year and at higher numbers than usual, said University of Illinois Extension entomologist Phil Nixon, who added the heat has probably contributed to their numbers.
Cicada killer wasps have been sighted throughout the state this week and last, including in several Arlington Heights parks, which has caused concerned parents to call the park district recently.
Male cicada killer wasps tend to be a pest for any human who walks through their aerial territories, hitting their heads into people to make sure they aren't a threat to their mates. But the lack of a stinger makes the male wasps harmless, Nixon said.
The real killers are the females. Between late June and mid-August they repeatedly find cicadas to paralyze with a sting. They then drag or fly the still-living cicada back to a burrow where they lay an egg on it.
When the egg hatches about two days later the larvae have fresh food waiting.
"They eat them alive," Nixon said, adding that there is debate among entomologists about how aware the cicada is of what is happening to it.
Anita Pacheco, superintendent of marketing and communications for the Arlington Heights Park District, said no park areas or playgrounds have been closed because of the wasps.
"They are not an aggressive form of wasps," she said. "It does have an intimidating name, but that's just to describe what they feed off."
While they appear to be menacing, female wasps are reluctant to sting, and will only do so if they are stepped on by a bare foot or grabbed by a bare hand, Nixon said. He said he has personally heard of fewer than five cases of people getting stung by a cicada killer wasp, and those people have told him it isn't very painful.
Cicada killers can cause damage to property, creating burrows that are between 7 to 20 inches deep in poor turf areas, such as along a sidewalk or near sand in a golf course -- or even sandboxes.
"They can move a considerable amount of soil," Nixon said.
Many of the concerned calls Nixon has received regarding the insect have come from residents in the Chicago metropolitan area.
"I try to convey to people these are not really a threat. You can live with this," he said, adding that the wasps tend to fade off in the second or third week in August.
But for people who just can't handle the killers, Nixon recommends using Sevin Dust or Delta Dust pesticide, which will kill the females and, in turn, cause the males to leave.
Nixon has heard of golf courses shutting down holes that have cicada killers near them simply because of the "intimidation to the golfers." But he thinks the fear is irrational.
"The biggest problem with this insect is between your ears," he said.