Bryan McAllister’s personal reference notebook
July 30, 2026Short & citedBlog
Civic Viewpoint.
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Kept by Bryan McAllister — short guides, clear facts, and the Canadian angle when it matters.
Field Notes • Insects

Boxelder bug

The boxelder bug is a true bug in the genus Boisea, best known as a nuisance insect around homes and buildings.

Updated July 30, 20261 min readCited sources

The boxelder bug is a true bug known as a nuisance insect around homes. It feeds mainly on boxelder trees and can gather in large numbers on buildings in autumn.

What it is

Adult boxelder bugs are flattened, elongated true bugs about 1/2 inch long. They are dark brownish-black with red or orange markings, including three red stripes on the thorax. They are commonly recognized by these markings.

Why it matters

Boxelder bugs are considered nuisance pests because large numbers may enter homes in autumn seeking overwintering sites. They do not damage buildings but can stain surfaces with droppings and release an unpleasant odor when crushed.

Key details

Boxelder bugs feed mainly on sap from boxelder trees, especially female or seed-bearing trees. They may also feed on other maples, ash, and some fruits. They are native to much of North America and are most noticeable in late summer and autumn.

In short

  • Boxelder bugs feed mainly on boxelder trees and other maples.
  • They are nuisance pests that often enter homes in autumn.
  • They do not cause structural damage but can stain surfaces.
  • They are native to much of North America.
Canadian angle

Boxelder bugs are found in Canada wherever boxelder trees and related maples occur, and they are a familiar nuisance insect in Canadian homes and landscapes.

Quick questions

What is a boxelder bug?
A boxelder bug is a true bug, Boisea trivittata, that feeds mainly on boxelder trees and is commonly encountered as a nuisance pest around homes.
Are boxelder bugs harmful to people?
They are not known to sting or transmit disease and are generally not known to bite, though rare defensive biting has been reported.
Why do boxelder bugs come into houses?
They often move into buildings in autumn to find protected overwintering sites and may gather on sun-exposed walls before entering.

Sources

  1. UNH Extension —
    Supports: Feeding habits, host plants, nuisance status, and physical description.
  2. UMN Extension —
    Supports: Overwintering behaviour, nuisance status, and attraction to buildings.
  3. USDA Forest Service —
    Supports: North American distribution, host association, and limited plant damage.
  4. NPIC —
    Supports: Nuisance nature, staining, odor when crushed, and lack of disease transmission.
  5. Cornell Cooperative Extension Ontario —
    Supports: Canadian relevance, overwintering behaviour, and host plant association.