Causal Agent:
The two species of bed bugs (Insecta:  Hemiptera:  Cimicidae) usually implicated in human infestations are Cimex lectularius and C. hemipterus.  Although rare, humans may become incidental hosts of Cimex species of bats and birds.

Life Cycle:

Adults and all nymphal stages of Cimex spp. need to take blood meals from warm-blooded hosts, which are typically humans for C. lectularius and C. hemipterus, although other mammals and birds can be utilized in the absence of a human host.  Female bed bugs lay about five eggs daily throughout their adult lives in a sheltered location (mattress seams, crevices in box springs, spaces under baseboards, etc).  Eggs hatch in about 4-12 days into first instar nymphs which must take a blood meal before molting to the next stage.  The bugs will undergo five nymphal stages ( , , , , ), each one requiring a blood meal before molting to the next stage, with the fifth stage molting into an adult .  Nymphs, although lacking wing buds, resemble smaller versions of the adults.  Nymphs and adults take about 5-10 minutes to obtain a full blood meal.  The adults may take several blood meals over several weeks, assuming a warm-blooded host is available.  Mating occurs off the host and involves a unique form of copulation called ‘traumatic insemination’ whereby the male penetrates the female’s abdominal wall with his external genitalia and inseminates into her body cavity.  Adults live 6-12 months and may survive for long periods of time without feeding.

Geographic Distribution:
Cimex lectularius is cosmopolitan in distribution; C. hemipterus is distributed in the tropics and sub-tropics.