Ladybugs Are Back: Warm Temperatures Trigger Swarms In Minnesota and Wisconsin

Warm fall weather is a cue to ladybug that it's ok to come out from the hidden crevices of doorframes and windows and enjoy life. As temperatures increased over the past couple of days in Minnesota and Wisconsin, millions of ladybugs barged in on homeowners, many of whom now consider the tiny insect an annoying pest.

"Yesterday I can honestly say I vacuumed up 100 of them in the house, all day long," Lori Bissell, of Knife River on Minnesota's North Shore, told MPR News. "I would just have the vacuum cleaner out. I'd see four or five, look away, and there would be four or five more. I just don't know how they get in."

These multicolored Asian lady beetles, which are orange, not red, are not native to the U.S. In fact, they are actually relatively new to American shores. One theory about how they made it here was that the U.S. Department of Agriculture (USDA) originally introduced them in 1900s to gobble up aphids plaguing fruit trees. However, since many entomologists believe this population didn't survive, others suggest the insects may have stowed away on cargo ships from Asia.   

These ladybugs are slightly larger than the more familiar red ones and they are often seen on warm autumn days when they seek aphids or plant lice to feed on. But when it starts to get colder, the ladybugs scurry back to their shelter, according to the University of Minnesota.

"Thousands of these insects would be trying to sneak in through gaps in siding, or around windows or door frames that don't quite seal properly," P.J. Liesch, director of the Insect Diagnostic Lab at the University of Wisconsin, told MPR News. "And they can just be quite a general nuisance."

These tiny insects can bite – causing minor illness in people and pets – and they may secrete a foul-smelling orange liquid if disturbed or squished, so it's better to leave them alone and wait for the colder temperatures to force them back into their warm hiding places. 

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