Boxelder Bug Identification — Black and Red Bugs on Your House?
Dozens of black bugs with red markings sunning themselves on your siding every fall? Upload a photo and our free AI confirms in seconds whether they're boxelder bugs or a look-alike.
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How to Identify Boxelder Bugs
Check these features before you rely on any single one — the combination is what confirms the ID.
Adults are about 1/2 inch long, black to dark grey, with three red or orange lines on the area behind the head and red lines along the edges of the wings. Their bright red belly shows when they fly.
Boxelder bugs are narrow and flat rather than round or shield-shaped, with wings folded flat over the back and crossing near the tip, the mark of a true bug rather than a beetle.
The young (nymphs) are smaller, wingless, and bright red, often mixed into the same clusters as adults. A group of red and black bugs together is a strong boxelder sign.
In September and October they gather in large groups on sunny, south- and west-facing walls, fences, and rocks to warm up before looking for a place to overwinter.
They feed mainly on the seeds of female boxelder trees, and also on maple and ash. If there's a boxelder or maple nearby, that's almost certainly where your bugs came from.
After overwintering in walls and attics, they wander into living spaces on warm winter and spring days, often around windows. They don't breed or feed indoors.
Boxelder Bug Look-Alikes
Boxelder Bug
Black with three red lines behind the head and red wing edges; nymphs bright red. Harmless to people, pets, and your house, though their droppings can leave small red-orange stains on curtains and walls.
Red-Shouldered Bug (Soapberry Bug)
Very similar black body, but with red only on the 'shoulders' and edges and red eyes. Common in the southern US around golden rain and soapberry trees. Also harmless.
Large Milkweed Bug
Orange and black in bold bands, with a black band across the middle of its back. Found on milkweed plants rather than clustering on houses. Harmless.
Small Milkweed Bug
Black with an orange-red X pattern across the back and white spots near the wing tips. Lives on milkweed and doesn't invade homes in numbers.
Milkweed Assassin Bug
Orange-red and black, but with a long narrow head, a curved beak tucked under it, and long spindly legs. A predator that can deliver a painful bite if handled, so don't pick it up.
Firebug (Europe)
Red and black with two black spots and a black triangle pattern, often clustered at the base of lime (linden) trees. Harmless and common across Europe.
Kissing Bug (Triatomine)
Dark body with a red, orange, or yellow banded edge, but with a cone-shaped head on a neck-like section. Bites sleeping people and can transmit Chagas disease. Capture it without touching and contact your health department.
Not sure what bug it is? Our free picture identifier identifies any insect, spider, or garden creature from a photo with the same AI.
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Frequently Asked Questions
Sources & References
Our identification guides are researched from the authorities below and reviewed by the IdentifyThis team. AI photo identification is a helpful starting point — for anything involving safety (venomous species, edibility, or medical symptoms), always confirm with a qualified expert before acting.
- CDC — Pest- and health-related guidance
- EPA — Integrated pest management
- UC IPM — University of California Pest Notes
- BugGuide — Entomology identification community
- Smithsonian — Insect & animal biology
Reviewed by the IdentifyThis team · Last updated August 2026