Adult body is gray-brown to black with three red lines on the pronotum and forewing; the abdomen is usually red. The small nymphs are bright red and become marked with black when about half grown.
Eggs are laid on the bark and leaves of the tree; total eggs per female are 200 to 300. Hatching occurs in 11 to 14 days. Development from egg to adult takes about 60 days, and there can be three generations per year. Adults and large nymphs of the last generation seek an overwintering site in late fall.
Food includes the seeds, leaves, and twigs ofboxelder and other maple trees, including silver maple, sycamore maple, and ash. This bug also will feed on young fruits such as apple, pear, peach, plum, and grape. Adults of the first generation feed on fallen boxelder seeds on the ground or on low vegetation. They feed on female boxelder and other maple trees once the seeds begin to form.
Habits. Overwintering occurs in large numbers around building foundations and ground-floor windows.
Boxelder bugs gather on the south and west sides of buildings where the sun heats exposed surfaces; they are sensitive to small temperature differences and select the warmest substrate. Adults are capable of flying about two miles to find a suitable overwintering site.
Winter harborage. Overwintering sites selected by the boxelder bug, kudzu bug, marmorated stink bug, and cluster fly usually are on east- or west-facing walls of buildings or attics. Overwintering insects can detect small differences surface temperature, and the radiant energy from the sun reaches these sides during half a day. Thus, these sides provide the greatest warmth in winter and quickly warm up in spring. Horizontal or Hat surfaces are warmest during the middle of the day.