Suddenly, the yellowjackets were everywhere.
The teenage pitcher got stung on the mound. We had yellowjackets swarming us on the sidelines and crawling into our beverages. No amount of loud, echoing-across-the-field swearing by my dad helped keep them away.
Maybe you’ve been having run-ins with yellowjackets lately in Michigan too.
It turns out, this is not a predatory social wasp apocalypse, but just normal yellowjacket behavior this time of year.
Sarah Hughson is the arthropod diagnostician (she helps people resolve their insect issues) with Michigan State University Plant and Pest Diagnostics. She said in late summer and fall, yellowjackets reach their peak populations in their nests.
“We're more likely to encounter them because there are more of them out. But another thing starts to happen this time of year. When we get into late summer and fall, some of their food resources start to decline. So they become stressed,” Hughson said. “And at this point, they're going to be more likely to approach people when they're searching for food.”
She said that means they're more likely to sting if they get agitated.
"If you're having, like, a picnic or a barbecue, the yellowjackets almost always show up. And that's because we're bringing everything they like to that party. So they like sweet drinks with sugar. They like, you know, the meat in your hamburger."
In their regular lives, when they’re leaving us alone, yellowjackets like flower nectar, or fruit that has dropped off of trees. They also collect protein for their babies.
“The larvae feed on protein-rich foods. So the adults will also collect meaty things. So they'll collect insects, things like caterpillars. They might also collect small bits of meat, and they'll take those back to the nest to feed their young,” said Hughson.
So that explains why they’ll swarm your hamburger.
How to avoid getting stung
Hughson said yellowjackets can sting you numerous times, unlike a honeybee.
“With something like a honeybee, they can really only sting you one time. And then the stinger usually pulls out of the insect. But with yellowjackets, that doesn't happen,” she said. “If you do ever get like a yellowjacket in your coat or something like that, you should take off that coat because they could be trapped in a sleeve or something like that, and sting you repeatedly.”
Hughson said the best thing you can do is try to avoid them. She said yellowjackets are attracted to sweet, sugary drinks and meat but also bright clothing and perfume.
So that might mean moving a BBQ indoors or into a screened-in tent, and trying not to look like a beautiful flower and instead choosing darker, drab-looking clothing (sounds like an awesome party).
In Michigan, she said, we have two main types of yellowjackets, and most of the yellowjacket species we have are native. They also help us out by eating other insects that can be pests in gardens.
“We have two genera of insects that are called yellowjackets. We have the ground nesting yellowjackets, and these are the Vespula. And these guys are going to be kind of black and yellow, and they're going to have stripes and they are going to nest in the ground. We also have another group called the aerial yellowjackets: Dolichovespula. And these are going to be things like the baldfaced hornet that live above ground. They're going to create those kind of paper football-shaped nests that we see in trees.”
So you could end up with the kind of yellowjackets in your yard that build nests in the ground, or the kind that build nests in trees.
“If you have, you know, a nest in a high traffic area where there's children, if there are people that are allergic to bees in the area, that's a time when you might want to spray that nest. If you have a nest in an area where you can avoid the yellowjackets, then sometimes it's better to just avoid them. Because when people do go out to spray the nest, that's another time when stings can occur,” she said.
Sometimes, yellowjackets will build nests in a hole in the side of a house, which can turn into a bigger problem.
“One thing I do like to warn people about is to make sure to not seal that gap while the nest is still active,” Hughson said. “If there's a nest in the side of a house and you seal that gap while they're still active inside, they're going to try to chew their way out. And sometimes they can find their way into the house, and that's when you have a situation that nobody's happy with.”
The good news here for humans?
As our nights get colder, yellowjacket populations will start to decline. Hughson said everyone leaves those nests and dies off.
Only the new queen of a colony will survive the long winter, tucking herself under leaf litter or tree bark.
