The yellow-striped, thumb-sized wasps have been buzzing yards and ball fields all over the western suburbs, their quirky behavior made all the more intimidating by their red transparent wings and big jaws.
Courtney Waltz was at Berens Park in Elmhurst on Saturday when she spotted the creatures.
"The wasps were by the dirt along the fences/dugouts," she said on Facebook.
“Cicada killers are relatively common and seem to be quite numerous this year,” Phil Nixon, an entomologist for the University of Illinois Extension. “They’re quite prevalent the second half of July and through much of August anyplace where they’re active.”
Area residents are reporting dozens of them flying around their back yards and digging holes. They look similar to the deadly giant Asian hornet, but Nixon said that highly unlikely.
“It’s popular to think any big wasp is the giant Asian hornet,” the entomologist said, “but there have been no verified sightings in North America.”
Cicada killers are solitary wasps, with the female digging a 6- to 10-inch burrow in the ground. The female grabs a cicada and stings it, then drags her prey back to the burrow. After laying an egg on the paralyzed prey, the larvae pupates, and emerges as an adult the next summer.
In general, the large wasps tend to avoid humans. The males cannot sting, but they will hover 2 inches in front of your face and intimidate the hell out of you. All females are interested in doing is finding a cicada, digging a hole and laying an egg, before repeating the process.
Nixon said females are reluctant stingers that must be severely provoked before they’ll sting someone. He’s only known of three instances where people got stung but one.
“Two grabbed one barehanded, and another stepped on it barefoot, but you really need to ask for it,” he said. “Once they figure out you’re not a cicada, they’ll leave you alone.”
The adult cicadas do little feeding and a lot of “singing,” when the males rub their legs together to attract female cicadas. The nymphs live underground on tree roots while pupating sucking the sap out of them. For that reason, the killer wasps may be handy to have around.
“We look at the cicada killers as beneficial to the ecosystem,” Nixon said. “We figure anything that eats a bug to be a good bug, it doesn’t matter what they eat. They’re relatively harmless once you get over the fear between your ears.”
Last summer’s drought may have contributed to this year’s large population of cicadas, which means more cicada killers.
“Another major mortality factor on cicadas is a fungal disease,” he said. “When you have a hot, dry July and August, more won’t get the disease and survive, which means more meat on the hoof for the wasps.”
Nixon doesn’t recommend trying to control the female cicada killers but to leave them alone. Since they tend to build their chambers in loose sandy surfaces like sand traps or on volleyball courts, Sevin dust is the preferred method for eradicating them.
Experts say cicada killers have been particularly prevalent around park ball fields, so it's no wonder Waltz was seeing them at Berens Park last weekend, at Field #5 at the first-base dugout.