Box elder bugs are black insects with red-orange markings that mass on sunny walls in fall and enter homes to overwinter. Common wherever box elder and maple trees grow around Whidbey and Fidalgo, they are a harmless but conspicuous nuisance.
How to identify box elder bugs
About 1/2 inch, black with distinctive red-orange lines on the body and wings. Nymphs are bright red. They gather in large, obvious clusters.
Behavior & season on Whidbey & Fidalgo
They feed on box elder and maple seeds in the warm months, then congregate on warm south and west walls in fall before entering to overwinter in voids, emerging again on warm days.
Why box elder bugs are a problem
They do not bite, sting, or damage the home, and their feeding rarely harms trees. The issue is purely the large, staining clusters and their habit of wandering indoors in winter.
Signs of box elder bugs activity
- Clusters of black-and-red bugs on sunny walls in fall
- Bugs indoors on warm winter days
- Concentrations near box elder or maple trees
- Staining where large groups gather
How Salty Dog treats box elder bugs
We treat exterior harborage and aggregation sites and seal entry points, focusing effort in fall when they are gathering to come inside. Learn more about our Box Elder Bug Control service, or browse the full Pest Library.
Reviewed by Matthew — Salty Dog Pest Control. WSDA-licensed structural pest applicator (License #101709). Veteran- and family-owned, serving Whidbey Island, Fidalgo Island, and west Skagit County.
Frequently asked questions
Do box elder bugs cause any damage?
No — they do not bite, damage the house, or meaningfully harm trees. They are strictly a nuisance in large numbers.
Why so many on one side of my house?
They gather on the warmest sun-facing walls in fall before moving inside. That warm-wall clustering is the time to treat and seal.
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