Cimex lectularius

Cimex lectularius and Cimex hemipterus, the two most common species, produce lesions that range from purpuric macules to urticarial erythematous papules. The classic presentation involves three bites in linear array, also known as “breakfast, lunch, and dinner” pattern. Lesions are commonly seen on exposed areas of the face, neck, hands, or arms. 902 In predisposed individuals, bullous lesions can be evident, which is due to a late-phase response to an IgE-mediated hypersensitivity to nitrophorin, an antigen present in the C. lenticularis saliva. 903,904

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

Clinical Presentation

Although bed bugs have been found naturally-infected with blood-borne pathogens, they are not effective vectors of disease. The primary medical importance is inflammation associated with their bites (due to allergic reactions to components in their saliva)

Sometimes referred to as red coats, chinches, or mahogany flats (USDA 1976), bed bugs, Cimex lectularius Linnaeus, are blood-feeding parasites of humans, chickens, bats and occasionally domesticated animals (Usinger 1966). Bed bugs are suspected to carry leprosy, oriental sore, Q-fever, and brucellosis (Krueger 2000) but have never been implicated in the spread of disease to humans (Dolling 1991). After the development and use of modern insecticides, such as DDT, bed bug infestations have virtually disappeared. However, since 1995, pest management professionals have noticed an increase in bed-bug-related complaints (Krueger 2000).

Figure 1. Adult bed bug, Cimex lectularius Linnaeus, feeding. Photograph by Joseph Smith, University of Florida.

Distribution (Back to Top)

Human dwellings, bird nests, and bat caves are the most suitable habitats for bed bugs because they offer warmth, areas to hide, and hosts on which to feed (Dolling 1991). Bed bugs are not evenly distributed throughout the environment but are concentrated in harborages (Usinger 1966). Within human dwellings, harborages include cracks and crevices in walls and furniture, behind wallpaper and wood paneling, or under carpeting (Krueger 2000). Bed bugs are usually only active during the night but will feed during the day when hungry (Usinger 1966). Bed bugs can be transported on clothing, and in luggage, bedding and furniture (USDA 1976). Bed bugs lack appendages that allow them to cling to hair, fur, or feathers, so they are rarely found on hosts (Dolling 1991).

Description (Back to Top)

The adult bed bug is a broadly flattened, ovoid insect with greatly reduced wings (Schuh and Slater 1995). The leathery, reduced fore wings (hemelytra) are broader than they are long, with a somewhat rectangular appearance. The sides of the pronotum are covered with short, stiff hairs (Furman and Catts 1970). Before feeding, bed bugs are usually brown in color and range from 6 to 9.5 mm in length. After feeding, the body is swollen and red in color (USDA 1976).

Figure 2. Dorsal view of an adult bed bug, Cimex lectularius Linnaeus. Photograph by David Almquist, University of Florida.

Figure 3. Lateral view of an adult bed bug, Cimex lectularius Linnaeus. Photograph by Joseph Smith, University of Florida.

Figure 4. Nymph of the bed bug, Cimex lectularius Linnaeus. Photograph by Joseph Smith, University of Florida.

The two bed bugs most important to man are the common bed bug, Cimex lectularius, and the tropical bed bug, Cimex hemipterus. These two species of bed bugs can be easily distinguished by looking at the prothorax, the first segment of the thorax. The prothorax of the common bed bug is more expanded laterally and the extreme margins are more flattened than that of the tropical bed bug (Ghauri 1973).

Life Cycle (Back to Top)

Because of their confined living spaces, copulation among male and female bed bugs is difficult. The female possesses a secondary copulatory aperture, Ribaga’s organ or paragenital sinus, on the fourth abdominal sternum where spermatozoa from the male are injected. The spermatozoa then migrate to the ovaries by passing through the haemocoel, or body cavity (Dolling 1991). The female bed bug lays approximately 200 eggs during her life span at a rate of one to 12 eggs per day (Krueger 2000). The eggs are laid on rough surfaces and coated with a transparent cement to adhere them to the substrate (Usinger 1966). Within six to 17 days bed bug nymphs, almost devoid of color, emerge from the eggs. After five molts, which take approximately ten weeks, the nymphs reach maturity (USDA 1976).

Survey and Management (Back to Top)

Bed bugs are most active at night, so their infestations are not easily located (Snetsinger 1997). However, when bed bugs are numerous, a foul odor from oily secretions can easily be detected (USDA 1976). Other recognizable signs of a bed bug infestation include excrement left around their hiding places (Dolling 1991) and reddish brown spots on mattresses and furniture (Frishman 2000). Good sanitation is the first step to controlling the spread of bed bugs. However, upscale hotels and private homes have recently noted infestations, suggesting that good sanitation is not enough to stop a bed bug infestation (Krueger 2000).

If bed bugs are located in bedding material or mattresses, control should focus on mechanical methods, such as vacuuming, caulking and removing or sealing loose wallpaper, to minimize the use of pesticides (Frishman 2000). The effectiveness of using steam cleaners or hot water to clean mattresses is questionable. Heat is readily absorbed by the mattress and does no harm to the bed bug. For severe infestations, however, pesticides may be used. Care should be taken not to soak mattresses and upholstery with pesticides. Allow bedding and furniture to dry thoroughly before using. One study shows that over-the-counter foggers are not effective for controlling bed bugs (Jones and Bryant 2012).

Selected References (Back to Top)

• Dolling WR. 1991. The Hemiptera. Oxford University Press, New York, New York.
• EPA. 2018. Bed bugs: get them out and keep them out. https://www.epa.gov/bedbugs. (12 March 2021)
• Frishman A. 2000. Bed Bug basics and control measures. Pest Control 68: 24.
• Furman DP, Catts E. 1970. Manual of Medical Entomology, 3rd ed. National Press Books, Palo Alto, California.
• Ghauri MSK. 1973. Hemiptera (bugs), pp. 373-393. In K.G.V. Smith [ed], Insects and Other Arthropods of Medical Importance. British Museum, London, England.
• Jones Sc, Bryant JL. 2012. Ineffectiveness of over-the-counter total-release foggers against the bed bug (Heteroptera: Cimicidae). Journal of Economic Entomology 105: 936-942.
• Koehler PG, Pereira RM, Pfiester M, Hertz J. (July 2011). Bed bugs and blood-sucking conenose. EDIS. (26 April 2017)
• Krueger L. 2000. Don’t get bitten by the resurgence of bed bugs. Pest Control 68: 58-64.
• Potter MF. (January 2010). Bed Bugs. University of Kentucky Entomology FactSheets. (26 April 2017)
• Snetsinger R. 1997. Bed bugs & other bugs, pp. 393-425. In Mallis A, Hedges SA [eds.], Handbook of Pest Control, 8th ed. Franzak & Foster Co., Cleveland, Ohio.
• Schuh R, Slater JA. 1995. True Bugs of the World (Hemiptera : Heteroptera) Classification and Natural History. Cornell University Press, Ithaca, New York.
• [USDA] U.S. Department of Agriculture. 1976. How to Control Bed Bugs. USDA. Washington D.C.
• Usinger RL. 1966. Monograph of Cimicidae (Hemiptera — Heteroptera). Entomological Society of America, College Park, Maryland.

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Discussion

Our results have shown that natural patterns of traumatic insemination carry a measurable fitness cost for female C. lectularius, thereby providing evidence that the conditions for a sexual conflict over the mating frequency are present.

Frequent remating by male bed bugs probably occurs, at least in part, because the pattern of sperm precedence (P₂ = 0.68) favors the last male to copulate. The observations of copulation, and the lack of any overt female resistance behavior during copulation, suggest that females have no behavioral control over mating frequencies. Indeed, the evolution of a piercing intromittent organ that bypasses the normal reproductive system may have provided males with the opportunity to avoid female adaptations that control copulation frequency. Females are unlikely to avoid traumatic insemination by dispersing away from areas where they encounter males given the sex ratios we observed in natural populations. Alternatively, multiple mating may provide fitness gains for females that offset, or exceed, the costs. Females that mate with several different males to get “good genes” or allelic diversity in their offspring may produce more viable offspring (24, 32). However, no viability differences were found in a suite of putative fitness traits in the offspring of singly or multiply mated female C. lectularius. Another possible benefit of multiple mating is that females may be avoiding genetically incompatible sperm that would lead to infertility of eggs or reduced offspring fitness (33, 34). Because no difference in the number of infertile eggs laid by the high- and low-mating group was found, this is also an unlikely explanation.

Our results indicate that females need to copulate only approximately once every four blood meals to maximize their lifetime reproductive success; the normal copulation rate (20 times the optimum) results in females suffering reduced longevity without a compensatory increase in egg-laying rates. This result mirrors the pattern of the mating cost in D. melanogaster (12). However, in D. melanogaster, the remating rate of females is influenced by female nutritional status [females thus have some control over their remating rate and therefore the expression of the mating cost (14)].

The mechanism that reduces longevity in female C. lectularius exposed to natural remating frequencies is not clear. The mode of copulation and insemination in C. lectularius produces potentially novel mechanisms for a cost of mating. Repeated copulatory wounding will result in the expression of cuticle-repair systems that are potentially costly in energetic terms (35) and so may divert resources away from somatic maintenance resulting in reduced longevity. Another cost of mating in C. lectularius may be associated with the need to respond to infection by pathogens introduced into the female as a consequence of traumatic insemination. Exposure to sexually transmitted diseases is a cost of mating that has been well documented in several taxa (36, 37), and it is likely to be an important cost in traumatically inseminating organisms because the intromittent organ is introduced directly into the female’s hemocele.