IPM Checklist
Boxelder Bugs: Nuisance Home Invader
The short answer
Boxelder bugs are oval, about half-inch, dull black insects marked with red or orange along the front wing edges that feed on boxelder and sometimes maple seeds in summer.
In fall they gather in masses on warm sunny surfaces, preferring white walls on the south side of buildings, and some work their way indoors to overwinter.
They are not harmful to people or pets, will not bite or reproduce indoors, and do not damage the house, though crushed bugs can stain fabrics.
Manage them by sealing entry points and knocking clusters down with soapy water; an insecticide is not necessary or recommended, and avoid spraying indoors.
Identification and where they come from
Adults are oval and about half an inch long, dull black and marked with red or orange along the edges of the front wings; nymphs are red.
They primarily feed during summer on the leaves, twigs and seeds of boxelder trees and sometimes other maples, so a nearby seed-bearing boxelder is often the source.
Why they cluster on your house in fall
In fall, typically around October, the red nymphs and black adults collect in masses, first on boxelder trunks near the ground and then on sunny building exposures.
The University of Maryland notes they congregate on porches, windows, door frames and siding and prefer white surfaces on the south side of buildings, where the warmth draws them before they seek cracks to overwinter in.
They are a nuisance, not a threat
The boxelder bug is not harmful to humans or pets, and it will not bite or reproduce indoors, so it poses no health or structural risk to the home.
The main drawbacks are cosmetic: reports indicate squashed bugs will stain fabrics, which is a reason to remove rather than crush them.
How to manage them
- 1Seal them out — Exclude bugs by caulking around windows and adding weather stripping around doors, focusing on warm south- and west-facing walls where they gather.
- 2Knock down clusters — Spray exterior aggregations with soapy water, and vacuum or sweep up any that get indoors and release them outside.
- 3Reduce the source — Where practical, removing nearby seed-bearing (female) boxelder trees can reduce local populations over time.
⚠ These are minor nuisance pests. The University of Maryland states an insecticide is not necessary or recommended; skip indoor spraying and rely on exclusion and physical removal.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Maryland Extension — Boxelder Bugs — Verifies oval half-inch dull black adults marked with red/orange along front wings; summer feeding on leaves, twigs and seeds of boxelder and sometimes maples; fall clustering (October) in masses on trunks and on sunny exposures, preferring white surfaces on the south side of buildings; that they are not harmful to humans or pets and will not bite or reproduce indoors; that squashed bugs stain fabrics; and that an insecticide is not necessary or recommended, with exclusion by caulking and weather stripping plus vacuuming/sweeping indoors.