Flat-backed, elongated and narrow box elder bugs are ½ inch long brownish black insects with three red stripes behind their head. Box elder bugs may invade buildings, especially during the warm days of autumn, to seek shelter sites for over-wintering. They are attracted to lights and will readily fly in open doors and windows. Indoors, these bugs are a nuisance, produce a foul odor when crushed–often causing them to be confused with stink bugs –and may stain curtains with fecal matter. Outdoors, they can be found clustering in large numbers on the sides of trees, buildings and other structures. Large populations are often correlated with long, hot, dry summers. During warm winter and spring days, they may become active, moving from their hiding places into living spaces. These bugs hide in cracks and crevices in walls, in door and window casings, around foundations, in stone piles, in tree holes and in other protected places. Although they do not cause damage to buildings, clothing, food or humans, populations are annoying.
Since box elder bugs feed and reproduce primarily on female box elder trees, removal of these trees, especially around the house, would eliminate nuisance populations. However, adults are capable of flying two or more miles for suitable hibernation quarters. You should eliminate potential hiding places such as piles of boards, rocks, leaves, grass and other debris close to the house. Rake leaves and grass away from the foundation in a six- to ten foot wide strip, especially on the south and west sides of the structure. Be sure to caulk and close openings where box elder bugs can enter the house such as around light fixtures, doors and windows, unscreened vents, holes in walls around utility pipes or conduits, air conditioners, heat pump lines and through the foundation. They are also attracted to lights and can fly in open doors or windows. Screen all windows, doors, crawl spaces, exhaust and roof vents and louvers.