Boxelder bugs (Boisea trivittata) are common insects that become household nuisances, particularly during the cooler months. These insects, recognizable by their black bodies and distinctive red markings, spend the majority of the year feeding and reproducing in trees. Their sudden appearance on or inside homes is a direct result of their biological needs changing with the seasons. Understanding the attractants that draw them to residential areas is the first step in managing their presence.
Primary Food Sources
The primary attractant for boxelder bugs is the presence of specific host trees, which provide their nutritional source. Their diet focuses heavily on the seeds, flowers, and tender leaves of a few tree species.
The female boxelder tree (Acer negundo) is their preferred host, as the bugs rely on its highly nutritious seeds for development. They cluster on these trees throughout the spring and summer to feed on developing seed pods and young twigs. This feeding establishes a large population near a potential shelter site.
While boxelder trees are the main food source, the bugs also feed on other members of the maple family, such as silver maple, and occasionally ash trees. They may also consume the fruits of plum, apple, or cherry trees, which can result in minor scarring of the produce. The proximity of these host trees during the active season is the fundamental reason a property becomes a boxelder bug habitat.
Seasonal Migration for Warmth
The attraction to a home shifts as the summer ends and ambient temperatures begin to drop. Boxelder bugs transition from feeding to seeking a suitable location for overwintering, a state of dormancy. This migration is triggered by shortening daylight hours and cooling weather, starting in late summer or early fall.
These adult bugs can fly up to two miles in search of a thermal refuge to survive the winter. They are strongly attracted to structures that offer maximum solar exposure, especially walls facing south or west. These sun-drenched surfaces absorb and retain heat, providing the insects with the warmth they need to prepare for hibernation.
The bugs congregate in large masses on these warm surfaces, absorbing the sun’s energy before they move into shelter. They seek a location where the temperature remains consistently above freezing but cool enough to prevent premature activity. The home serves as a staging area before they find an entry point.
Ideal Structural Shelters
Once boxelder bugs arrive at a structure, their attraction focuses on physical characteristics that provide secure, insulated shelter from the cold. They utilize their small, flat bodies to squeeze into the tiniest openings to reach a protected overwintering site.
The insects seek out any structural defect or gap that offers access to wall voids, attics, or crawl spaces. Common entry points include cracks in the foundation, loose-fitting window and door frames, and gaps where utility lines or pipes penetrate the exterior walls. Small openings, such as those around soffit vents or under loose siding, are sufficient for mass entry.
Though the color of a house is not the primary attractant, materials that better retain heat, such as stone or brick, can make a structure more appealing. The ultimate goal is to find a dark, quiet cavity where the temperature remains stable, allowing them to remain inactive until spring. Sealing these structural vulnerabilities is the most effective measure to prevent the seasonal influx.