Cimicidae, commonly known as bed bugs, are small parasitic insects that feed on the blood of humans and other warm-blooded animals. They are wingless and have a flat, oval-shaped body, ranging in color from brown to reddish-brown. Bed bugs are nocturnal and hide in cracks and crevices during the day, emerging at night to feed on their hosts. Their bites can cause skin irritation and allergic reactions in some individuals.