Bed bugs are parasitic insects of the cimicid family that feed exclusively on blood. Cimex lectularius, the common bed bug, is the best known as it prefers to feed on human blood although other Cimex species are specialized to other animals, e.g., bat bugs, Cimex pipistrelli (Europe), Cimex pilosellus (western US), and Cimex adjunctus (entire eastern US).
The name of the “bed bug” is derived from the preferred habitat of Cimex lectularius: warm houses and especially nearby or inside of beds and bedding or other sleep areas. Bed bugs are mainly active at night, but are not exclusively nocturnal. They usually feed on their hosts without being noticed.