Boxelder Bug Identification & Control
Boisea trivittata
Every fall, Plainfield homeowners see the same alarming sight: hundreds of dark bugs with red markings congregating on the sunny south and west walls of their.
Quick Identification
- Size: About ½ inch long
- Color: Black with distinctive red-orange markings including three stripes behind the head; wings form a red V-pattern when folded
- Key Features: Aggregates in large numbers on warm, sunny exterior walls in fall; overwinters in wall voids and attics; associated with boxelder and maple trees
- Active Season: Fall (invading) and early spring (emerging from overwintering)
- Risk Level: None — nuisance only; does not bite, does not damage structures or food
The Fall Wall Swarm
Every fall, Plainfield homeowners see the same alarming sight: hundreds of dark bugs with red markings congregating on the sunny south and west walls of their homes. These are boxelder bugs, and while they look concerning in large numbers, they’re completely harmless.
Boxelder bugs spend spring and summer feeding on the seeds of boxelder trees (a type of maple). As temperatures cool in fall, they seek warm, protected overwintering sites — and the sun-warmed exterior walls of homes are ideal gathering spots. The bugs release a chemical scent that attracts more boxelder bugs to the site, which is why numbers can build rapidly. From exterior walls, they find their way through cracks and gaps into wall voids, window frames, attics, and basements where they’ll remain dormant through winter.
On warm winter days, boxelder bugs may emerge inside your home, sluggishly crawling on walls and windows as they’re “fooled” into thinking spring has arrived. They don’t feed on anything indoors, don’t reproduce inside, and don’t bite. However, their feces can stain fabrics, walls, and carpets, and crushed bugs leave red stains and an unpleasant odor. Vacuum them rather than squishing them.
Prevention is the key: seal cracks and gaps in your home’s exterior before fall. Dispersing aggregations with a water hose before they enter also helps. Our quarterly pest control program includes exterior perimeter treatments timed to reduce fall invader entry. Contact Sanctuary Pest Control at 815-993-3472.
Related pests
Sources: Illinois Department of Public Health (dph.illinois.gov) — Occasional Invaders; University of Illinois Extension — Boxelder Bug.
Spotted boxelder bug at your home?
Free inspection — we ID the species, confirm the issue, and give you a fixed quote before any treatment.