In the next few weeks we can expect to see large numbers of multicolored Asian lady beetles (called Harmonia axyridis in Latin or the Halloween ladybug). I have good news and bad news; first, the good news. Both adult and young lady beetles (called larvae) feed on large numbers of insects that attack plants. Each alligator-like larva can eat around 300 aphids (which feed on many types of plants) before becoming an adult.

The bad news is that multicolored Asian lady beetles enter houses in the fall to hibernate. On warm days, the beetles may become active and move to other parts of the house. They do not do any structural damage and neither feed nor reproduce while inside. They may stain walls and fabrics when disturbed, by forcing drops of their strong-smelling blood out of their joints. These insects may occasionally bite and can, in rare instances, cause an allergic reaction.

The best way to manage this home invader is to “build it out” by caulking around cracks and crevices, making sure window screens are in good repair, covering exhaust vents with 20-mesh screen, and making sure that doors seal properly. Once inside the home, Asian lady beetles can be removed using a vacuum cleaner. A nylon stocking can be used to catch the beetles before they enter the vacuum cleaner bag. With the vacuum cleaner turned off, push the stocking into the end of the hose, leaving enough outside the hose to seal the stocking in place using rubber bands. After vacuuming, the stocking can be tied off and the beetles disposed of.

Colin Stewart is an Integrated Pest Management Specialist at the University of Maine Cooperative Extension in Orono. For more information about insect or plant diseases, call 581-3880, or 1-800-287-0279 toll-free (in Maine).