The multicolored Asian lady beetle (Harmonia axyridis), has become common throughout the United States and all of Iowa. It is well known for the annoying habit of accumulating on the sides of buildings and wandering indoors during the fall. Asian lady beetles are a beneficial biological control in trees during the summer, and in fields and gardens during the fall, but can be a severe household nuisance during late fall and winter. Wooded residential and industrial areas are especially prone to problems.
The origins of the Asian lady beetles are not clear, although it appears the current pest species was not purposefully released in the United States or in Iowa. Beetles that arrived by accident in ports such as New Orleans in the late 1980s have crawled and flown all by themselves to all corners of the country.
Asian lady beetles, like other accidental invaders, are “outdoor” insects that create a nuisance by wandering indoors during a limited portion of their life cycle. They do not feed or reproduce indoors; they cannot attack the house structure, furniture, or fabrics. They cannot sting or carry diseases. Lady beetles do not feed on people though they infrequently pinch exposed skin. Lady beetles may leave a slimy smear and they have a distinct odor when squashed.
Asian lady beetles follow their instinctive behavior and fly to sunny, exposed surfaces when preparing to hibernate through the winter. The time of beetle flight varies but is usually from mid-September through October (depending on weather). Light colored buildings and walls in full sun appear to attract the most beetles