Boxelder bugs are common insects that feed on sap from the trees of the maple family. Large numbers of them can be seen on tree trunks and branches, or sunning themselves on the south and west sides of buildings in the spring and fall. These harmless accidental invaders may be a temporary nuisance as they move into and out of sheltered overwintering sites in the fall and spring.
As time passes from summer the Boxelder bugs move to sheltered areas (including nearby houses and buildings) in the fall and remain there during the winter. Not to worry though as they will not multiply or infest any household articles. These insects are only a nuisance or accidental invader; however, they may leave an odour and stain when crushed so it is best to treat outside and kill them before they can get in.