In most parts of the United States the only bed bug of importance to man is Cimex lectularius. Bed bugs feed on blood, mostly from people in this species but are also known to feed on bats or other animals including rabbits, rats, guinea pigs and domestic fowl, especially when they are housed in laboratories. The bed bug has a sharp beak which it uses to pierce the skin of the host. It then begins feeding, injecting a fluid which helps in obtaining food. This fluid causes the skin to become swollen and itchy.
Bed bugs are nocturnal, that is, they feed at night, often biting people who are asleep.
Where infestations are severe one may detect an offensive odor which comes from an oily liquid the bugs emit. A bug which has recently fed is engorged with blood, dull red in color, and the body is elongated and swollen. Newly hatched bugs are nearly colorless. The young are called nymphs. When fresh, the eggs are coated with a sticky substance which causes them to adhere to any object on which they are deposited.