The boxelder bug (BEB) is a common and well-known insect that is most abundant after summers when the month of May is very warm and July is very dry. However, the abundance varies greatly from place to place as well as from year to year. There are some BEB problems even in years when a widespread outbreak does not occur.
During the summer months, BEBs live, feed and reproduce on trees, shrubs and other plants (including boxelders, maples, ashes and others). They feed on sap from their host plants but do not cause significant damage. BEBS become nuisance pests in the fall when they leave the plants to find hiding places for the winter.
During their random search, they congregate in the sunshine on the south sides of buildings, trees and rocks. From there they stray into houses through cracks in the foundation and siding, gaps along windows and doors, and other small openings. BEBs within walls or attics remain inactive while they are cold. The nuisance occurs when the ones warmed by heat from the furnace or the sun become active during the winter and crawl into the rooms.
BEBs do not reproduce indoors. They only lay eggs on trees and other plants. BEBs do not feed indoors. They are sap feeding insects with a beak that can only suck liquid food (sap) from the twigs and seeds of selected species of trees and shrubs. BEBs are harmless as they can not damage the house, its furnishings or occupants. They can be, however, a considerable nuisance.