Colored scanning electron micrograph (SEM) of the head of a bedbug (Cimex sp.). It has a compound eye (grey) on each side of its head. Antennae protrude on either side of its mouth. The stylet, a piercing mouthpiece (red, center,) is used to suck blood from warm-blood animals, including humans. Bedbugs are generally only active at night, hiding in crevices in walls and furniture and in bedding during the day. Although they do not transmit disease, their saliva can cause itchy swellings on the skin.