The Cimicidae are a highly derived family of cimicomorphan bugs, some of which are known as bedbugs. They are known from all zoogeographic regions. The family is considered to be indigenous to all regions except Australia, where the synanthropic human bedbug, Cimex lectularius Linnaeus, is undoubtedly introduced. The majority of species occur in the Afrotropical and Oriental regions, with the speciose genus Paracimex occurring also in New Guinea. The family contains 24 genera and 110 species (Usinger 1966; Slater 1982; Zoological Record 1980–1994; Henry 2009).
The morphology of the Cimicidae is highly specialised for their ectoparasitic niche. The body is dorso-ventrally flattened, ovate or elongate-ovate, and often clothed with bristle-like setae. The eyes are present and ocelli are absent. The antennae are short and 4-segmented; the two distal segments are slender. The labium is 4-segmented but appears 3-segmented. The pronotum is characterised by lateral projections bordering the eyes. The forewings are reduced to coriaceous pads and the hind wings are absent. The scent efferent system is reduced; the larvae have dorsal abdominal scent glands between terga III–IV, IV–V and V–VI. The tarsal formula is 3:3:3 and the pretarsi lack pulvilli (Slater 1982).
All cimicids are non-permanent ectoparasites of birds and mammals. They are generally associated with the roosts and nests of their hosts. Human bedbugs are most commonly collected in cryptic microhabitats of human dwellings, such as cracks in walls. Three species, Leptocimex boueti Brumpt, Cimex hemipterus (Fabricius) and Cimex lectularius Linnaeus, have been recorded feeding on humans. Sailer (1952) speculated that the association arose from the cohabitation in caves of man, bats and bugs. Permanent dwellings, characteristic of later human civilisation, were ideal for the association and eventual synanthropy.
Considerable information is available on the biology of the Cimicidae, although most pertains to Cimex lectularius. Usinger (1966) reviewed their biology, including nutrition, feeding behaviour, oviposition and natural enemies. Bedbugs have been implicated in the transmission of human diseases such as filariasis, kala-azar, anthrax, pneumonia, poliomyelitis and smallpox. However, no conclusive evidence exists for the sustained transmission of these diseases by bedbugs (Usinger 1966).
Cimicids, like some anthocorids, are characterised by traumatic and extragenital haemocoelic insemination. This entails the male puncturing the body wall of the female with a copulatory organ and injecting sperm into a system of structures loosely called the spermalegé. Sperm then migrate via the haemocoel to the base of the lateral oviducts where they are stored in the seminal conceptacles (Carayon 1966; Davis 1966).
Usinger's (1966) classification includes six subfamilies: Primicimicinae (Primicimex Barber and Bucimex Usinger—bat parasites from the Nearctic and Neotropical regions); Cimicinae (Bertilia Reuter, Cimex Linnaeus, Oeciacus Stål, Paracimex Kiritshenko and Propicimex Usinger—bird, bat and human parasites from all biogeographic regions); Cacodminae (Cacodomus Stål, Aphrania Jordan & Rothschild, Loxaspis Rothschild, Stricticimex Ferris & Usinger, Leptocimex Roubaud and Crassicimex Ferris & Usinger—bat parasites from the Old World tropics, subtropics and temperate regions excluding Australia); Afrocimicinae (Afrocimex Schouteden—pteropodid bat parasites from the Afrotropical Region); Latrocimicinae (Latrocimex Lent—bat parasites from neotropics); and Haematosiphoninae (Ornithocoris Pinto, Caminicimex Usinger, Psitticimex Usinger, Haematosiphon Champion, Cimexopsis List, Synxenoderus List and Hesperocimex List—bat and bird parasites from the Nearctic and Neotropical regions).
Southwood and Leston (1959) broadened the concept of Cimicidae to include the Anthocoridae. Ford (1979) and Schuh and Štys (1991) indicated a closer relationship between the Cimicidae and the Xylocorini and Almedini. Ford (1979) provided a monophyletic definition of the Cimicidae based on loss of ocelli, microptery, temporary parasitism of homeothermous vertebrates, dilated anteclypeus and broadly flattened body. These authors did not resolve the placement of the Xylocorini and Almeidini, which were retained within the Anthocoridae by Cassis & Gross (1995).
Carayon, J. 1966. Chapter 7. Traumatic insemmination and the paragenital system. pp. 81-166 in Usinger, R.L. (ed.). Monograph of Cimicidae (Hemiptera—Heteroptera). Baltimore : Horn-Shafer.
Davis, N.T. 1966. Chapter 8. Reproductive Physiology. pp. 167-178 in Usinger, R.L. (ed.). Monograph of Cimicidae (Hemiptera: Heteroptera). Baltimore : Horn-Shafer.
Ford, L.J. 1979. The Phylogeny and Biogeography of the Cimicoidea (Insecta: Hemiptera). Unpubl. Masters thesis. Storrs : University of Connecticut vii 138 pp.
Sailer, R.I. 1952. The bedbug. An old bedfellow that's still with us. Pest Control 20: 22, 24, 70, 72
Schuh, R.T. & Štys, P. 1991. Phylogenetic analysis of Cimicomorphan family relationships (Heteroptera). Journal of the New York Entomological Society 99: 298-350
Slater, J.A. 1982. Hemiptera. pp. 417-447 in Parker, S.P. (ed.). Synopsis and Classification of Living Organisms. New York : McGraw Hill Book Co.
Southwood, T.R.E. & Leston, D. 1959. Land and Water Bugs of the British Isles. London : Frederick Warne & Co. Ltd xi 436 pp., 32 col. pls, 31 monotone pls.
Štys, P. 1982. A new Oriental genus of Ceratocombidae and higher classification of the family (Heteroptera). Acta Entomologica Bohemoslovaca 79: 354-376