While the Twin Cities basked in summery temperatures Sunday, the rapid warm-up also produced a surprise invasion: a species of Asian ladybugs that descended on some neighborhoods by the thousands.
The autumn ambush of the Asian lady beetle hit “big-time” on Sunday, said Stacy O’Reilly, president of Plunkett’s Pest Control in Fridley. “They come in incredible numbers.”
The record warm day — following several chilly nights — set the ladybugs on the march for a place to spend the winter, O’Reilly said.
“One actually bit me yesterday while I was at my folks’ bed-and-breakfast near Hinckley,” she said. O’Reilly said calls have been flooding in to her extermination company in many of the 10 Midwestern states where it does business.
With its orange-red body and black dots, the Asian lady beetle resembles the native ladybug popular in children’s books and magazines. But an “M” marking on the head sets it apart.
“The good news is they won’t do any damage to your walls,” O’Reilly said. “They won’t reproduce, and they won’t eat anything.”
The Asian lady beetle was imported from China to the Deep South to consume aphids, then in the mid-1900s migrated north to Minnesota “in huge numbers,” said Val Cervenka, a forest entomology expert with the state Department of Natural Resources.
During the summer, they are often welcomed in the Midwest because they eat aphids (plant lice) that threaten soybeans and other crops, O’Reilly said. As they detect winter’s approach, they are “looking for things that stand out” as a place to live until spring, Cervenka said.
“A light-colored house facing south is likely to attract a lot of lady beetles,” she said.
Most homeowners don’t panic on finding a handful in their house, O’Reilly said. But “an inch thick on a windowsill — that’s a problem.”
The beetles also seem to come in cyclical waves, O’Reilly said. “We’ll have a monster year, then a quiet year, and then a monster year.”
Though it catches many Midwesterners by surprise, the bugs do bite, Cervenka said.
“They are sort of tasting you. ‘Is this food?’ ”
She said they also emit a foul smell to ward off predators. “If you vacuum them, it smells.”
Infestations were much worse years ago, Cervenka said.
“I remember [when] you couldn’t even hang laundry outside.”
Stephen Kells, an entomologist for the University of Minnesota Extension specializing in insects that penetrate structures and stored food, found himself studying the bugs firsthand on Sunday.
“We had them all over our house,” said Kells, who lives in Lino Lakes. “I’m not too sure why our particular house. … They were well into the hundreds.”
Turning lemons into lemonade, Kells’ daughter captured some of the invaders and added them to her insect project for school.