Boxelder bugs are black with reddish or orange markings on their back. Adult boxelder bugs are about half an inch long and have a body shape that is a somewhat-flattened and elongated oval. They have six legs and two antennae that are typically half of their body length. Nymphs look similar to adults but lack wings and are bright red in color. In order to prevent boxelder bugs from invading homes, repair holes in window and door screens, seal cracks and crevices with a good quality silicone or silicone-latex caulk, and install door sweeps to all exterior entrances.
When getting rid of boxelder bugs that have already entered a home or building, no attempt should be made to kill them in wall voids because dead insect bodies can attract dermestid beetles (larder beetles, carpet beetles, etc.). We recommend waiting until summer when all live overwintering adults are out of the wall voids. To provide temporary relief during this time, consider using a vacuum cleaner to get rid of the boxelder bugs. The bag should be removed to prevent the bugs from escaping.
Treatment for boxelder bugs is on a seasonal basis. The exterior of the home can be treated with an insect growth regulator (IGR) just before the overwintering adult boxelder bugs emerge from hibernation. Boxelder bugs emerge in late March to early April when boxelder tree buds open. A similar treatment can be applied to nearby harboring tree trunks during mating months, which are late May to late August. Right before the fall migration, your home and surrounding building(s) can be treated around windows, door vents, and any open cracks and crevices to control interior infestations.