Wasps are known to crash Midwestern summer barbecues. But this year, there are so many buzzing around that picnickers are being forced indoors or left doing the dance of the distressed, furiously swatting at the stinging insects.
Known colloquially as yellow jackets, the wasps this year showed up earlier in the region — and they’re sticking around longer, too.
The Midwest had a fast start to spring, with warmer-than-average temperatures in March and April. Those conditions met wasps’ nest-building criteria, so they had more time to lay more eggs, according to experts.
And as colonies outgrow their nests, the wasps are on the hunt for food.
“Now you’re seeing them go after your sodas and your beers and your wines and all that sugary stuff,” said Adam Hintzke, who runs the Bug Man and Queen Bee, a Milwaukee exterminator business, with his wife, Chandell. “That’s why now they are so bad, and everyone’s noticing.”
His company’s call volume related to wasps has shot up by 30 percent starting in spring. Hintzke said he treated one property this year on a quarter-acre lot that had five yellow-jacket nests in the ground.
“Previous to this year, it would be highly unlikely to find two yellow jacket colonies on the same property around the Milwaukee area,” he said.
About 90 miles west, Steph Martin has seen the expansive patios at Buck & Honey’s restaurant near Madison sit vacant lately — even on sun-splashed days.
“People don’t really want to be out there with them,” said Martin, the restaurant’s general manager. “We ended up having tables [of people] sit out there and then move inside. In general it has not been a good patio summer for us.”
Hintzke said there were 50 new requests for service, all wasp-related, after the long Labor Day weekend. It’s a somewhat overwhelming volume for his four-person crew, but they expect the requests to continue for weeks.
It has been a warm September for the area — and with no early frost risk, the milder temperatures could last deep into October.
Other exterminators in the region aren’t even answering their phones, with voicemails explaining they’re booked out into next July.
Warmer weather fuels breeding
The surge in the wasp population comes in part because of weather trends related to climate change: shorter and less frigid winters, warmer summers and more rainfall.
Every colony starts from just one queen that goes into a type of hibernation in winter and emerges to grow a colony when the weather allows.
The earlier a queen can establish a nest, which Hintzke said takes at least a few days of temperatures in the mid-40s, the longer she has to expand the colony as she lays eggs and hatches young workers.
Warmer winters also mean higher survival rates for queens. More queens mean more nests and bigger populations.
In spring, newly hatched wasps are protein-hunters. They go on a slug-and-bug quest to feed the queen, which needs the extra boost for egg-laying and rearing the newcomers.
Later in summer, wasps’ missions shift to quests for carbohydrates. Hence the interest in sugary drinks and other food.
Fears of home invasion
Unlike their bee relatives, yellow jackets can sting more than once. But they’re not necessarily looking to use those stingers, said Emily Laub, an evolutionary biologist at the University of Illinois who has studied wasp behavior for about eight years.
Despite their activity interrupting cookouts and other outdoor meals, she said wasps aren’t “setting out to ruin your day.”
“They’ve kind of got their own business to attend to, if that makes sense,” she said. “They’re definitely motivated to protect their home, just like you’re motivated to protect yours.”
Wasps use their stingers only when they feel threatened, she said. With humans, that fear often arises for an expected reason — people accidentally wandering close to a nest that they probably don’t know is there. But there’s another fear factor that’s less understood: carbon dioxide coming from human breath.
To the tiny fliers, carbon dioxide in the air signals another living thing, and they can’t necessarily differentiate between who’s producing it, be it a potential predator or a harmless human. It can trigger their defensive reflexes.
For those seeing more nests on their property this year, Laub has some practical advice.
“If I get up really close to a nest to see what’s going on in there, I will actually hold my breath or breathe away from the nest,” Laub said. “So, move slowly and breathe away from them.”
Ben Noll contributed to this report.
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