The common name, Boxelder Bug, reflects the fact that this species is a major pest of boxelder trees. Boxelder Bugs are primarily a nuisance pest because they enter structures to overwinter.
Boxelder Bugs are also commonly found in “swarms” on the exterior of homes and other structures, typically attracted to the south and west sides due to the warmth of the sun. Boxelder Bugs are native to the Western states, but are now found throughout the United States wherever boxelder trees are found.
Adult Boxelder Bugs are about 1/2” long, flat and oval, black in color with reddish lines on their back. When the Boxelder Bug flies, their bright red abdomen is visible from underneath their wings.
The overwintering Boxelder Bug adults emerge from hibernation and the females lay clusters of straw-yellow eggs on stones, leaves, grass, shrubs and trees, especially in the bark crevices of boxelder trees. These eggs turn red as they develop and are ready to hatch in about 2 weeks. The Boxelder Bug nymphs feed on fallen seeds and new leaves. In the warmer regions of the United States, there can be two generations per year.
The primary host plant of the Boxelder Bug is the seed-bearing boxelder tree, but they can also occur on the seed-bearing maple and ash trees as well, which are quite common here in the northwest. Occasionally the Boxelder Bug will feed on the fruits of plum and apple trees.
In the autumn, Boxelder Bugs congregate on the south side of trees, rocks, and buildings where the sun hits. After large masses congregate, they may fly to nearby buildings to hibernate for the winter.
Inside, Boxelder Bugs are primarily a nuisance pest. However, their fecal material may cause a red stain, resulting in discoloration on curtains, drapes, clothing, and other resting places. When crushed or handled roughly, they produce a strong, disagreeable odor.
Control of the Boxelder Bug begins outside. Reducing the outdoor population of the Boxelder Bug is highly recommended. Reduction is achieved by spraying infested areas of siding on the home or building as well as infested deck surfaces and should be done by a trained and licensed pest control operator. Additionally, spraying infested trees and ground covers around the infested trees can help reduce future infestations of Boxelder Bugs.