About Boxelder Bugs

What Are Boxelder Bugs?

Boxelder bugs (Boisea trivittata) are true bugs in the order Hemiptera, native to North America. Adults are about half an inch long with a flat, elongated body, dark brown to black coloring, and three reddish-orange lines on the thorax with red edging along the wings. Their eyes are large and red.

Nymphs are wingless and nearly entirely bright red when first hatched. Black markings develop gradually as they mature. If you spot small vivid red insects near a boxelder or maple tree, those are almost certainly boxelder bug nymphs.

Boxelder bugs are sometimes confused with stink bugs since both invade homes in fall and emit an odor when crushed. They are different species. Stink bugs have a broad shield-shaped body; boxelder bugs are slender with distinctive red striping.

Where Do Boxelder Bugs Come From?

Boxelder bugs are closely tied to their host trees. Their primary food source is the female boxelder tree (Acer negundo), which produces the seed pods they feed on. They also feed on maple, ash, and occasionally fruit trees including apple, peach, pear, and plum.

Properties with mature female boxelder or silver maple trees see the highest populations. Because adults can fly up to two miles, a tree on a neighboring property can still drive activity on yours. Populations tend to be larger after hot, dry summers, which favor faster nymph development.

Life Cycle and Seasonal Behavior

Boxelder bugs develop through three stages: egg, nymph, and adult. The full cycle spans approximately one year.

Spring: Overwintered adults emerge, feed for about two weeks, then mate. Females lay clusters of small rust-red eggs in bark crevices or on leaves. Eggs hatch in 10 to 14 days.

Summer: Nymphs pass through five molting stages over roughly 50 to 78 days, developing wings and adult coloration by late July. A second generation develops through late summer into fall.

Fall: Adults congregate in large numbers on warm, sun-exposed surfaces, particularly south- and west-facing walls, before seeking overwintering sites. They can travel several miles to find shelter.

Winter: Bugs overwinter inside wall voids, attics, and other protected cavities in a dormant state. They do not feed or reproduce during this period.

Why Are They in My House?

Boxelder bugs enter homes strictly to survive winter. They are not attracted to food, moisture, or structural decay. Common entry points include cracks in foundations and siding, gaps around window and door frames, torn screens, and openings around utility penetrations.

Once inside, they move into wall voids and other undisturbed spaces and remain inactive until spring. They do not nest or build any structure. Homeowners typically notice them reappearing along window frames and baseboards as temperatures rise in late winter.

If host trees and entry points remain unchanged, boxelder bug pressure will return each fall.

Are Boxelder Bugs Dangerous?

Boxelder bugs are nuisance pests, not health or structural threats.

• Biting: They are not known to bite. Their mouthparts are designed for piercing plant material. Rare reports of defensive pricking exist but cause no injury.
• Disease: They do not transmit disease to humans or animals.
• Structural damage: They do not chew wood, damage insulation, or compromise any structural material.
• Staining: Their feces can leave reddish-brown spots on light-colored walls, curtains, and upholstery, particularly when large numbers die inside a wall void.
• Pets: Boxelder bugs are not toxic but taste foul. Dogs or cats that eat them may vomit shortly after. The reaction is temporary.
• Odor: They release a mildly unpleasant smell when crushed. Vacuuming is preferable to crushing when removing them indoors.