The overwintering adults emerge from hibernation when the boxelder buds open and fly back to their host trees, typically in late April to early May. They first feed on the fallen boxelder seeds and later move to the female boxelder trees when the seeds begin to form, feeding on the newly developing leaves.
In the autumn, boxelder bugs become gregarious and congregate on the south side of rocks, trees, and buildings where the sun hits. After large masses congregate, they may fly to nearby buildings to hibernate for the winter.
Inside, boxelder bugs are primarily a nuisance pest. However, their fecal material may cause a red stain, resulting in discoloration on curtains, drapes, clothing, and other resting places. When crushed or handled roughly, they produce a strong, disagreeable odor. They occasionally “bite” people, causing a skin irritation and producing a red spot similar to a small ulcer.