Stink Bug vs Boxelder Bug: Which Is in Your House?

Look at the stripes and the antennae. Boxelder bugs are dark with three red-orange stripes on the thorax and red-orange wing margins. Brown marmorated stink bugs are mottled brown, with light and dark bands on the last two antenna segments. Both come indoors in fall. Neither damages the house.

The two-second check

• Stripes across the back? Boxelder bug.
• Banded antennae and a broad, shield-shaped body? Brown marmorated stink bug.
• Bright red young ones? Boxelder bug nymphs.
• Yellowish young ones with black and red mottling? Stink bug nymphs.

If the insect is on a south-facing wall in October and there is a boxelder tree nearby, it is probably a boxelder bug. If it is on a window screen and there are fruit trees or a garden nearby, it is probably a stink bug. Neither guess replaces the stripe and antenna check.

Where they come from

Boxelder bugs feed on boxelder trees, especially seed-bearing female trees. Penn State Extension notes that in heavily infested areas they are sometimes found on ash and maple too. They gather in large numbers on the south side of trees, buildings and rocks in fall, then work into cracks in walls.

Brown marmorated stink bugs feed on a long list of shade trees, fruit trees and ornamentals. They are native to East Asia, were first confirmed in Allentown, Pennsylvania, in 2001, and are now a crop pest in much of the country. In fall they seek shelter in buildings, much like boxelder bugs and Asian lady beetles.

Do they bite, stain or smell?

Boxelder bugs cause no direct damage to the structure, contents or occupants of a building. The problem is the number of them. Penn State notes that thousands can enter a home, and that they do not reproduce indoors.

Brown marmorated stink bugs also do not reproduce inside or damage structures. Their smell becomes noticeable when many are crushed or pulled into a vacuum cleaner. Penn State adds that crushing one against exposed skin can cause dermatitis in a small percentage of people.

Nothing in the extension guidance used here describes either insect as a biting pest, and neither is treated as a staining problem. The harm is nuisance, plus crop damage from the stink bug outdoors.

No insecticide is needed inside a wall void or attic. Penn State advises against it for both insects, because dead bugs can attract carpet beetles.

Which one needs action?

Both need the same action: keep them out. Seal cracks around windows, doors, siding, utility pipes, chimneys and under the wood fascia with good-quality silicone or silicone-latex caulk. Repair damaged screens. Vacuum the ones that get inside.

The difference is what the insect means. The boxelder bug is a nuisance that clusters on warm walls. The brown marmorated stink bug is an agricultural pest that feeds on fruit and vegetables outdoors, and a nuisance indoors. One is a siding problem; the other is a farm and garden problem.

Exterior insecticide sprays break down in sunlight and give only short-lived control. If you use one, follow the product label; the label is the law. Sealing the openings works longer.

For the blood-feeding look-alike that can carry Chagas disease, see stink bug vs kissing bug. For the species profile, see brown marmorated stink bug. For the other pairs, see look-alikes. For insects by category, see insects.