Cimex lectularius Linnaeus, 1758
Bed bug (English), Bedbug (English), Punaise des lits (French)
The two species of bed bugs (Hemiptera: Cimicidae) usually implicated in human infestations are Cimex lectularius and C. hemipterus. Humans may also rarely become incidental hosts of Cimex species that normally fed on bats and birds. Although C. lectularius has a cosmopolitan distribution, C. hemipterus is limited to the tropics and sub-tropics.
The bed bug Cimex lectularius is a member of the family Cimicidae, a group of true bugs that are highly specialized for feeding on blood, mainly that of humans, birds, and bats. All these hosts occur in temporally and spatially predictable, gregarious assemblages in or around enclosed spaces such as caves or buildings and all have a relatively high body temperature. Cimex lectularius has been closely associated with humans for thousands of years (it is one of several cimicid species for which humans are the primary host). Despite this close association, however, it survives well on bird, bat, and rabbit hosts in the laboratory (in fact, it produces more eggs, and the hatched nymphs develop faster, when reared on mice, a host rarely encountered in nature) and has been found in the wild on several different bird and bat hosts. Nymphs of C. lectularius die within a few days of hatching if they do not feed and egg production ceases soon after adult females are prevented from feeding. Cimicids all mate by traumatic insemination, during which the male pierces the female’s abdominal wall (see Reproduction). (Reinhardt and Siva-Jothy 2007 and references therein)
There appears to have been a dramatic increase of C. lectularius in the developed world--notably in North America, Europe, and Australia--beginning in the 1980s or 1990s, particularly in hotels. Reinhardt and Siva-Jothy (2007) suggest that although these increases are facilitated by cheap air transport and increased travel, they are probably exacerbated by the disappearance of folk knowledge of these insects in the developed world. For example, most people under age 50 in the developed world have no ability to recognize (e.g., by smell) bed bugs and to take early measures to control infestations of these insects. (Reinhardt and Siva-Jothy 2007 and references therein) Another important factor in the recent resurgence in bedbug infestations in human dwellings seems to be the widespread evolution of resistance to commonly used pesticides (Romero et al. 2007).
Adults and all nymphal stages of Cimex species 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. (Centers for Disease Control Parasites and Health website)
Conservation and Management
Efforts to improve the reliability and efficiency of bed bug detection have led to the more widespread use of dogs trained to detect bed bugs. Pfiester et al. (2008) investigated the effectiveness of well trained dogs in bed bug detection. Dogs learned to detect as few as one adult male or female bed bug or five viable bed bug eggs. The authors found that the dogs were able to discriminate bed bugs from carpenter ants (Camponotus floridanus), cockroaches (Blattella germanica), and termites (Reticulitermes flavipes) with a 97.5% positive indication rate (i.e., correct indication of bed bugs when present) and 0% false positives (i.e., incorrect indication of bed bugs when not present). The dogs also were able to discriminate live bed bugs and viable bed bug eggs from dead bed bugs, cast skins, and feces, with a 95% positive indication rate and a 3% false positive rate for bed bug feces. In a controlled experiment in hotel rooms, dogs were 98% accurate in locating live bed bugs. Chemically extracted bed bug scent was recognized by trained dogs as bed bug scent in 100% of trials. The use of such "pseudoscents" could facilitate training and periodic testing of detector dogs.
Passive dispersal is the most important route by which wingless cimicids reach new hosts. Bed bugs can be transported by humans in clothing, luggage, and furniture. They may be unknowingly transported by people traveling by foot, car, train, ship, and airplane. (Reinhardt and Siva-Jothy 2007 and references therein) Bedbugs disperse easily within and between human dwellings. Wang et al. (2010) investigated a bedbug infestation in Indianapolis, Indiana (U.S.A.). They found bed bugs hiding in electrical outlets, in corners of ceilings, and behind baseboards on the floors. Bedbugs may migrate between apartments via walls or ceilings as well as by traveling between apartments through their front doors, as was documented repeatedly by Wang et al. Wang et al. found that half the residents in infested apartments were unaware of their infestations. These residents were either not sensitive to bed bug bites or mistakenly attributed bed bug bite symptoms to other causes. Five hundred and fifty-one bed bugs were trapped in one apartment within a 4-week period. The resident in this apartment was a frequent traveler (>4 travel days per week) and was not aware there were bed bugs in the apartment. Another resident used a bed bug-infested wheelchair in the building's common areas on a daily basis and was regularly visited by social workers and friends in his apartment, even though he was aware of the bed bug infestations.
Female bedbugs may take blood meals that are greater than 300% of their unfed weight. Male mating success is highest when female resistance is lowest, i.e., during feeding. Males prefer mating with inflated females and this is so whether they are inflated naturally with a blood meal or experimentally inflated with air (in these experiments, artificially inflated females reportedly return to their original size within less than 2 days). During mating, the male mounts the female without any apparent courtship and positions himself on her back. He then lowers the tip of his abdomen, from which a sclerotized, needle-like intromittent organ is expanded. This organ is pushed through the female body wall, the penis is guided through the intromittent organ, and sperm are ejaculated into a secondary female genitalic organ called the spermalege. This unusual copulation method is known as "traumatic insemination". The spermalege is entirely distinct from the primary female genitalia, the vagina, which is never used in mating but functions in oviposition (Reinhardt et al.  argue that the spermalege evolved as a female adaptation to reduce costs imposed by pathogens introduced during traumatic insemination). Within 2 to 6 hours of copulation, the sperm emigrate from the spermalege into the female hemolymph and migrate through the female oviduct into either the ovaries, where they fertilize the eggs, or into a secondary storage organ, the seminal conceptacles. (Reinhardt et al. 2009 and references therein) Females receive approximately five traumatic inseminations (not necessarily from the same male) per blood meal, which is about 20 times the insemination rate that would maximize their lifetime reproductive success. This higher insemination rate results in females suffering reduced longevity without a compensatory increase in egg-laying rates. Thus, females mate at a rate that is harmful to them, suggesting some degree of coercion by males. The explanation for the association between number of mating events and reduced longevity is uncertain but is likely related at least in part to the unusual mode of copulation. (Stutt and Siva-Jothy 2001)
Goddard and deShazo (2009) reviewed the literature on human health impacts of bed bugs. Although bed bugs have at various times been suspected of transmitting dozens of human diseases, there is little evidence supporting these beliefs. Reaction to bed bug bites is generally very minor or nonexistent, with no more than a barely visible puncture evident at the location of the bite. A variety of skin reactions (often itchy) may be seen (and an individual's reaction may worsen with increased exposure), but these symptoms normally resolve with no treatment within a week. Systemic reactions appear to be rare.
Despite the fact that bed bugs appear not to be disease vectors, bed bug infestations cost many millions of dollars annually in detection and control efforts by the hotel industry, the poultry industry, and private and communal households. Complex consequences resulting from bed bug infestations on poultry farms include loss of productivity due to allergic reactions of workers, reduced egg value due to bed bug fecal spots, reduced egg production from affected chickens, and increased feed consumption. (Reinhardt and Siva-Jothy 2007 and references therein)