Boxelder Bugs Invade Homes in Fall

Summary: Boxelder bugs are notorious in some areas for their yearly "visitations" on certain houses. The bugs are harmless but cause great irritation among these unfortunate homeowners.

Boxelder bugs, sometimes called maple bugs, are relatively large insects, about 1/2" long, dark gray in color with red markings on their backs (right). They are harmless. What makes these insects remarkable is their tendancy to congregate on houses in the fall of the year, often in enormous numbers. It truly seems like an invasion -- especially the first time it happens.

Here's what's going on. Boxelder bugs have one generation a year. Eggs are laid in early summer on maple trees. Eggs hatch and the young nymphs feed on maple tree leaves during the summer. By fall the insects have reached adulthood with fully developed wings and are ready to migrate in search of a protected place to spend the winter.