I know that ladybugs are supposed to be the good guys (or gals) but they’re all over inside my house. What happened? We used to see ladybugs occasionally outside but in recent years they’ve become indoor pests big time! My neighbors say the same thing.

C. L., Nottingham, NH

You’re right. When I was growing up, ladybugs were seen and appreciated only occasionally. Things began to change back in 1994 when we first noticed a new species of ladybug in New Hampshire, Harmonia axyridis, otherwise known as the multicolored Asian lady beetle (the “bugs” are actually beetles). Some say that the lady beetles arrived as stowaways on ships, from Asia of course. Another story says they were purposely introduced to control crop pests.

Meet the Multicolored Asian Lady Beetle

The multicolored Asian lady beetle is different than our native ladybugs in appearance and habits. They come in a range of colors. In New Hampshire, most are orange to reddish-orange or tan, with black spots in numbers ranging from none to 18. They are sometimes called “Halloween ladybugs,” probably because of the pumpkin color. The one characteristic that identifies this particular lady beetle is the black M-shaped marking on its back just behind the head.

Once in the U.S., populations of this new lady beetle mushroomed and quickly moved into new areas, often displacing native lady beetles. This newcomer, like all ladybugs, is primarily beneficial because both the adult and the larva feed on plant pests such as aphids and whiteflies. It is most often found in crop fields or in fruit trees and farmers generally love having them around. However, in some cases, the beetles have turned to feeding on the very fruits they are supposed to protect!

This Ladybug is an Overwintering Pest in Homes

For homeowners, the problems occur in the fall when the crops are senescing and the lady beetles move away from the fields, looking for protected places to spend the winter (see Lady Beetles Will Soon Move Into Homes). They can congregate on the sunny side of houses and other buildings in very large numbers, thanks in part to a pheromone that they release that attracts others.

Lady beetles will move into your home, sometimes by the hundreds or even thousands, if they can find an opening around doors, windows, or the roofline. Air conditioners are another common entry point. Once inside, the beetles eventually go into hiding in wall voids, attics, behind baseboards, wherever they can find a protected place. They may be roused out of their slumber though by unusually warm winter days. They’re not the perfect houseguests though since they can stain surfaces, they have a foul defensive smell, and they even sometimes bite…just a little nip.

Often people don’t want to kill the beetles since they are beneficial, so the best control is pest-proofing of your home to keep them out in the first place (see Keeping Fall Pests Out – Advice From the Pros). Although it may be too late to keep beetles out this year, we can set up a pest management program for you aimed at fall-invading insects that move in for the winter. Sealing openings that these pests use to get inside is just one of our jobs. Give Colonial Pest a call today.