Halloween-colored beetles near homes are a sign of autumn
Swarms of what appear to be ladybugs popping up recently on porches and windows aren’t Mother Nature's Halloween decorations.
The orange-and-black-spotted beetles are also not ladybugs. But the bugs — multicolored Asian lady beetles — are known to find the nooks and crannies of homes during the fall as the harvest season pushes them out of their summertime homes.
“This time of year we’re seeing more of them in towns and cities because the adults are looking for a place to spend the winter,” said Christopher Dietrich, state entomologist with the Illinois Natural History Survey. “They do kind of gravitate toward structures.”
After spending the spring and summer in corn and soybean fields, farmers harvesting their crops in the fall disrupt the insect’s living arrangements. The colder weather also causes them to search for crevices they can burrow into for warmth.
In fields or forests, the beetles tend to look for dead trees or logs with loose bark where they can make themselves warm and hibernate for the winter.
“But in the absence of that, they tend to go into people’s houses through cracks and crevices, and around the windows and doors, and so they end up inside and people start noticing them because they can show up in large numbers,” Dietrich said.
The multicolored Asian lady beetles are “basically harmless,” Dietrich said, but they can be a nuisance if they end up inside homes or buildings. And if handled roughly, the beetles can produce a foul-smelling, orange fluid that can stain carpets.
Dietrich’s best recommendation for anyone facing a swarm of beetles in their home?
“Vacuum them up, stick them in a bag and just put them out in the trash,” he said.
They should be that simple to deal with, and they don’t pose any other serious threats, he said.
But on a much larger scale, the multicolored Asian lady beetle does cause several concerns for biologists.
The species, which can be found across the U.S. and in parts of Canada, is not native to North America.
They were introduced to the area by the U.S. Department of Agriculture first in 1916 and again in the 1960s through 1990s as an attempt to control crop pests. Its population has grown as entomologists say the insect doesn’t have any natural predators.
“It was an intentional introduction that just kind of got out of hand,” Dietrich said.
Recent population increases are thought to have derived accidentally from a cargo ship in Louisiana, according to a Penn State University study.
One more complication: The multicolored Asian lady beetle is cannibalistic.
“We have a lot of native ladybug beetles in our state, and they’re becoming a lot less common because one, they’re being displaced by this nonnative species, and two, they’re actually being eaten by these Asian lady beetles,” Dietrich said.
Dietrich said that a nonnative species disrupting native species’ lives poses a long-term concern for the environment.
“So, getting rid of them is not a bad idea,” he said.