The boxelder bug, Boisea trivittata, lives outside but may invade homes as temperatures cool in the fall each year. This bug is distinctive in its appearance and coloration (Figure 1). Adult bugs are about 1/2-inch long and 1/6-inch wide. They are black with red lines on the back of the body. One red line runs along each side of the body and diagonal red lines are found on each wing. Immature bugs are mostly red with black only on the head, legs and front of the body.
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