True bugs, boxelder bugs are in the family Rhopalidae. Often confused with other other true bugs including the small milkweed bug and squash bug, boxelder bugs are distinguished by their black color and three lengthwise red stripes. Young nymphs are bright red. They turn black when about half-grown. The abdomen of both nymphs and mature boxelder bugs is a bright red. The eggs of the boxelder bug are a bright yellow when first laid and become a deep red as the nymphs inside develop.
Boxelder bugs do not sting or bite. They are not harmful to people or pets; however, they emit a very unpleasant odor when crushed. Indoors they stain clothing, curtains, counters and other surfaces with excrement.
Overwintered female boxelder bugs lay eggs in the crevices and cracks of the boxelder tree’s bark in early spring. The nymphs mature quickly and hatch in just a few days. The numphs mature into adults during the summer. They mate and lay more eggs that hatch into second-generation nymphs. In autumn, boxelder bugs gather in vast numbers on the south side of trees and buildings. Nymphs and adults migrate in large groups, covering tree trunks, fences and the walls of homes and other buildings in close proximity to boxelder trees. They often crawl under siding or cracks in home foundations, seeking a warm spot for winter hibernation. During winters, boxelder bugs often appear on light painted surfaces outdoors. They prefer a south or southwestern exposure warmed by the winter sun.
When boxelder bugs are migrating, keep windows and doors closed to prevent entry. Seal cracks and crevices in siding and window frames. Vacuum indoor surfaces to reduce interior bug population. Remove the vacuum bag and dispose of outdoors. Avoid smashing boxelder bugs. The odor is pungent, intense, unpleasant and long-lasting. if boxelder bugs are a continual irritation in your home, consider removing female boxelder trees on your property.