Boxelder Bug

The boxelder bug belongs to the family Rhopalidae (scentless plant bugs), order Hemiptera, and is native to North America. It gets its name from its close association with boxelder trees (Acer negundo), a species of maple, though it also uses other maples and ash trees as hosts.

The species is notable primarily for its striking fall aggregation behavior, when large numbers gather on tree trunks, rocks, and building exteriors, making it one of the most recognizable seasonal true bugs in much of the United States.

Despite its conspicuous swarming habit, its feeding on plant seeds generally causes little lasting harm to host trees.

• Elongated oval body, black background color with red-orange markings forming three stripes on the pronotum
• Red veins visible on the folded, membranous wings
• Four-segmented antennae; six legs
• Body length roughly 11–14 mm; nymphs are bright red and wingless
• Lookalike is the red-shouldered bug, a similar rhopalid, but the boxelder bug's specific striping and strong association with boxelder/maple trees are distinguishing

Native to North America; found wherever boxelder, maple, or ash trees grow, across much of the United States and southern Canada. Feeds on tree seeds and foliage during the growing season, then forms large sunning aggregations on trunks, rocks, and sunny exterior walls in autumn before seeking overwintering shelter.

Feeds primarily on developing seeds of boxelder and other maple trees using piercing-sucking mouthparts, occasionally feeding on fallen fruit as well. Highly gregarious, forming large sunning aggregations especially in fall. Feeding generally causes minimal damage to host trees. Considered a nuisance mainly when large numbers enter buildings to overwinter; it does not feed while sheltering indoors.

Incomplete metamorphosis. Eggs are laid on or near host trees in spring. Nymphs — bright red and wingless — develop through several instars over summer. One to two generations occur per year depending on climate, and adults overwinter in leaf litter, bark crevices, or structures.