Ladybugs like to snuggle up in your house over the winter, here's why.
Why You See Ladybugs in Your House during Winter
February 16, 2018
Complaints about ladybugs
One ladybug is cute. But a dozen feels like an infestation. When the cooler months set in, North Carolina State University entomologist Mark Waldvogel starts fielding calls from people complaining about the polka-dotted red beetles on their windows, plants and furniture.
“I’ve had people threatening to send me vacuum cleaner bags full of ladybugs,” he says.
Escaping the cold
Ladybugs, or lady beetles, escape the cold by tucking themselves into crevices on rocks and tree bark. But in urban areas, houses are an attractive alternative. They wriggle through weather stripping around windows or cracks in the wall. Then, ladybugs snuggle in groups to hibernate for the winter.
But on warm winter days, they often rouse themselves. “If you see them in your house during the winter, it’s likely they’ve already been there since the fall and a warm day has made them more active,” says Waldvogel.
Ladybugs are attracted to light
Waldvogel says ladybugs are attracted to light-colored, flat surfaces like windows.
“There’s been a lot of research showing that lady beetles have pretty good eyesight,” he says. “They see contrasts well, so they’ll notice the shutters around the window.”
Southeast-facing windows are particularly attractive, because they warm faster and brighten up first in the morning.
Getting rid of ladybugs is not easy
Waldvogel often has to disappoint callers determined to rid their houses of ladybugs. He said trying to spray each ladybug with pesticides isn’t practical or healthy, and light traps aren’t consistenly effective. Squishing a ladybug might not be a great idea either. Ladybugs produce defensive chemical secretions that stain, and sometimes cause allergy-like reactions in people.
But if a ladybug is active in the winter, it will likely die without a supply of aphids (their main source of food) to eat. Sometimes ladybugs will land on people and test them with a nip (Waldvogel says entomologists avoid the word “bite”). But ladybugs don’t want to eat you, says Waldvogel. “Ladybugs aren’t stupid. It’s not as if they think you’re a giant aphid.”
Keeping your house sealed tight against ladybugs (and cold weather) seems to be the most effective strategy, says Waldvogel. If they survive the winter, ladybugs will leave the house in the spring to lay their eggs on the underside of leaves.
The species of ladybeetle we’re used to seeing is originally from Asia (although we do have a native ladybug), and was deliberately released by the United States Department of Agriculture to control aphids. “Once they are outside, we advise people to leave them alone,” says Waldvogel. “They’re doing you a favor by eating all the aphids.”
- Rossie Izlar
Rossie Izlar is the associate producer of Sci Tech Now North Carolina, a weekly show highlighting the latest science stories from North Carolina and across the nation.