Probably everyone has seen ladybugs in the garden or on milkweed plants. They are well known and there seems to be plenty of literature about them, including poems for children; we may have many friendly encounters with them when young, and there are likely many entomologists out there who had a ladybug crawl on their arm when they were kindergarten age. Ladybugs are harmless, and they are beneficial because they prey on aphids, a farm and garden pest.

There is one species in the ladybug family, however, that can be a bit of a nuisance. The Asian lady beetle (Harmonia axyridis) appears to be a normal ladybug during the summer. The lady beetles eat aphids and appear on plants that attract aphids, such as milkweed.

The nuisance factor comes into play around this time of year as this species seeks openings in man-made structures to winter. They may appear in large masses on the sunny sides of buildings as they seek an opening to enter the dwelling or barn. Once in the house, they seek protected areas such as attics or between walls.

There is a misconception that the Asian lady beetle is poisonous. They are not poisonous, but their blood (hemolymph with insects) is foul smelling; if crushed or handled, the foul odor will be evident. This is a defensive mechanism used to deter potential predators. The aromatic compounds in the hemolymph have been known to cause an allergic reaction in a small number of people. The beetles can bite as well, but the bite is a small pinch; it’s best not to handle them both to avoid this and the foul smell. Soap and water will wash away the odor.