Madison Mysteries: Winter ladybug invasion

The mystery: Where did all these fucking ladybugs come from? While cockroaches get all the praise for tenacity, here in South Central Wisconsin we’re becoming increasingly familiar with another of nature’s great survivors: the ladybug. Every year, as the leaves and the temperatures start falling, some Madisonians find their homes teeming with ladybugs that trundle along windowsills and buzz around the overhead lighting.

The solution: Although hundreds of distinct insect species fall under the umbrella term “ladybug,” the ones that are currently infiltrating local homes are probably multicolored Asian lady beetles, says Phil Pellitteri, head of the insect diagnostic laboratory at UW-Madison’s entomology department. “These insects are native to eastern Asia and were imported to the US to control aphids as early as 1915. However, they were never found to be very effective, so eventually farmers stopped importing them. I’d say around 1997 multicolored Asian lady beetles unofficially became the most hated pest in the state,” Pellitteri observes. “It’s not uncommon for me to get calls from people who are using snow shovels and shop vacs to clean them out. Although the numbers now are coming into some kind of balance with nature, between about ’95 and 2000 my phone almost literally never stopped ringing with questions about them.”

Our current thriving strain of multicolored Asian lady beetle supposedly entered the U.S. accidentally through the ports of New Orleans and gradually began spreading across the country. The MALB is slightly more orange in color than the classic ladybug and generally features 19 black spots on its wing covers. The reason they’re currently congregating in our homes is that they need a warm place to spend the winter.

“In Asia these insects often overwinter on southeast-facing cliffs,” says Pellitteri. “So here, if the sun hits the southeast face of your house, they will be attracted to that. One thing that’s unusual about these insects is that they like to bite. I don’t think they do it because they’re ‘mean,’ so to speak, I just think they’re so hungry they taste just about anything they land on.”

Another unpleasant feature of the MALB is that, when harassed, they can secrete a small portion of their blood through their joints. This blood has an unpleasant smell, can stain furniture and walls, and has even been known to cause allergic reactions in some people. Pellitteri says the best way to keep the bugs out of your home is to seal around your windows, doors and utility openings. If the insects gather on outer walls, try spraying the south, west, and eastern sides of your home with a repellent in early fall.