Box elder bug (Boisea trivittata) is a North American species of true bug in the family Rhopalidae. The insect is native to the western United States, where it frequently infests maple and boxelder trees. From spring to fall, box elder bugs congregate on plants, sometimes in large quantities. As temperatures drop in Autumn, box elder bugs will invade households and other buildings, where they can become a nuisance.
Distribution & Habitat
Box elder bug commonly occurs from eastern Canada, south to the eastern United States, and west to eastern Nevada.
Box elder bug primarily infests maple and seed-bearing boxelder trees. It also occasionally infests and feeds on the fruit of plum and apple trees.
Immature nymphs are 1/16 of an inch long. The nymphs are initially bright red. As they mature, the nymphs increase in size, and darken in color. The adults measure around ½ inch in diameter. They are elongate to ovate in shape. The adults’ body is black, with orange or red markings, and three red stripes that appear on the prothorax, the area located behind the head. The head is narrow, while the body is relatively flattened. Long antennae protrude outwards from the head. The insect has piercing mouthparts, which enable it to extract plant fluids from leaves. The wings lay flat over the insect’s body, overlapping to form an ‘X’. The edges of the wings display red veins.
The adults emerge from their overwintering sites in early spring. They navigate to host trees, where they feed on plant material until early summer. By mid-summer, the adults begin to mate. Once fertilized, the females fly to seed-bearing boxelder trees, where they lay eggs on trunks, branches, seeds, leaves, and fruit. The eggs hatch a few days later, revealing masses of nymphs that initiate feeding on nearby plant material. The nymphs feed until fall, rapidly increasing in size. Mature nymphs will briefly pupate, before transforming into adults.
From late summer to fall, the adults vacate their host trees to find suitable locations to overwinter in. Many adults will overwinter in households, and other buildings, concealing themselves within small cracks and crevices. Nymphs that have not reached maturity by fall will typically perish during the winter months. The adults reappear the following spring, beginning the cycle anew.
Symptoms of Infestation
When populations are dense, the nymphs can be observed crawling on the ground, dwelling in gardens, and feeding on the plant material of host trees. Box elder bugs tend to aggregate on the southern and western exposures of tall structures and isolated buildings. As temperatures plummet in fall, the adults may penetrate into the interior of households, and other buildings. If disturbed, box elder bugs will expel a pungent compound, which can leave a reddish-orange stain on walls, curtains, and furniture. The insect’s mouthparts can puncture skin, causing a slight irritation, with a red spot arising in the center of the affected area.
- Repair holes in windows and doors to prevent entry to the adults.
- When the insect is present within a building, avoid fumigating. The husks of the dead insects will attract dermestid beetles, which can be destructive pests.
- Use a broom or a vacuum to remove expired box elder bugs from households. Dispose of them in a trash bag or vacuum bag.
- Residual insecticides can be employed in spring and fall to deter the adults from landing on buildings.
- A solution composed of ½ cup of dish soap and 1 gallon of water can be used to eliminate box elder bugs on plants, and the exterior of buildings.
Photo courtesy of Katja Schulz CC-by-2.0