The boxelder bug (Boisea trivittata) is a common North American insect often recognized as a nuisance pest by homeowners. Adults are easily identifiable by their slender, approximately half-inch-long black bodies marked with distinct reddish-orange lines on the thorax and along the edges of the wings. They are true bugs that feed on plant fluids.
The Boxelder Bug Diet
Boxelder bugs do not consume wood, nor do they cause structural damage to homes or other wooden structures. Their mouthparts are designed for piercing and sucking, not for chewing solid materials like wood. Their diet centers on the seeds and leaves of their namesake, the box elder tree (Acer negundo), but they also feed on maples and ash trees. While their feeding can sometimes cause minor distortion to new foliage, they are generally not considered a serious pest to the health of their host trees.
Why Boxelder Bugs Gather Near Buildings
The motivation for boxelder bugs gathering near homes is shelter, not food, as they are seeking a place to overwinter. Their sudden appearance in late summer and early fall is a seasonal migration driven by a drop in outdoor temperatures. The insects are attracted to warm, sun-exposed surfaces, often clustering on the south and west-facing walls of buildings. They use the sun-warmed exterior walls to raise their body temperature before attempting to enter a structure. Once inside the wall voids, attics, or under siding, they become inactive until they are disturbed or warmed up, which is why they sometimes appear indoors during winter.
Management Around the Home
The most effective way to manage boxelder bugs is to prevent their entry into the home before they begin their overwintering search in the fall. Homeowners should inspect and seal any potential entry points around the exterior of the house. This includes caulking cracks and gaps around window frames, utility pipes, and fascia boards that are an eighth of an inch or larger.
For bugs already found inside, physical removal is the recommended, non-chemical approach. A vacuum cleaner is the simplest tool for safely removing the insects without crushing them. Crushing them should be avoided because they release a foul odor and a fluid that can stain light-colored fabrics and walls. If host trees are close to the structure, removing fallen seeds and trimming branches away from the house can also reduce local populations.