Evolution of traumatic insemination


As can be seen in the figure above traumatic insemination occurs in only a small number of taxa but occurs in all members of the bed bug family. 

Within the True Bugs (Heteroptera) traumatic insemination occurs in the Prostemmatinae (Nabidae) and the Cimicoidea (Anthocoridae, Plokiophilidae, Lyctocoridae, Polyctenidae and Cimicidae), and has recently been discovered in the plant bug genus Coridromius (Miridae). Bed bugs are members of family Cimex, the most well-known of the family being Cimex lectularius which feeds on humans, and has been known to do so since the 17th century. Cimex hemipterus, found in tropical regions (including Florida) infests poultry and bats, and Leptocimex boueti, found in the tropics of West Africa and South America infests bats and humans. Cimex pilosellus and C. pipistrella primarily infest bats, while Haematosiphon inodora, a species of North America, primarily infests poultry.

Although the evolutionary background of C. lectularius is not very well studied as of late, we know of primicimex where females lack any traces of a spermalege altogether, and then stricticimex wherein the ectospermalege is well developed and the mesospermalege essentially forms a complete and complex copulatory tube leading to the oviducts, such that ejaculate does not come into direct contact with the hemolymph.

female bods

Some variation on traumatic insemination does exist between genuses. Remarkably, in the genus Afrocimex both males and females possess functional external paragenitalia, and males have been found with copulatory scars and the ejaculate of other males in their haemolymph. There is a widespread misbelief that males inseminated by other males will in turn pass the sperm of both themselves and their assailants onto females with whom they mate. We are not sure yet as to why males may choose to inseminate other males, although it seems like a failure of recognition.

In closely related Cimex hemipterus males require a blood meal before copulating and females require a blood meal before they oviposit. Males will then mate with females repeatedly.