Adult boxelder bug
Photo: Joseph Berger, Bugwood.org
The boxelder bug (Boisea trivittata) is an American species of true bug, also commonly known as the box elder bug or maple bug. It is found primarily on boxelder trees, as well as other maples and ash trees. They are generally not noticed during summer, but often can become an issue when they try to move into homes during fall as they search for overwintering sites.
Adult boxelder bugs are about 1/2-inch long, black with orange or red markings, including three stripes on the prothorax, the area right behind the head. Their wings lay flat over their bodies, overlapping each other to form an 'X'. The immature nymphs are 1/16th-inch long and bright red when they first hatch. As they grow older and become larger, they are red and black. You can potentially see all stages at any given time during the summer.
Adults and immature nymphs
William M. Ciesla, Forest Health
Mgmt International, Bugwood.org
During late summer and fall, boxelder bugs start to leave the trees from where they were feeding to find protected areas for the winter. Although nymphs may be present in the fall, only fully grown adults survive the winter. Adult boxelder bugs typically can fly several blocks, although in some cases they can travel as far as two miles. Some years they are more numerous than other years.
Boxelder bugs are harmless. They do not bite or sting and they are not attracted to food like ants. They are part of nature. They will become inactive when the weather turns cold enough.