Twin intromittent organs ofDrosophilafor traumatic insemination

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Abstract
In several animals, male genitalia create insemination wounds in areas outside the genital orifice of females. I report that such traumatic insemination (TI) occurs in theDrosophila bipectinatacomplex (Diptera: Drosophilidae) and illustrate a previously unknown evolutionary pathway for this behaviour. Flash fixation of mating pairs revealed the dual function of the paired claw-like basal processes, previously misidentified as a bifid aedeagus: (i) penetration of the female body wall near the genital orifice and (ii) sperm transfer into the genital tract through the wounds. Basal processes in closely related species (Drosophila ananassaeandDrosophila pallidosa) also wounded females but did not transfer sperm; this represents a transitional state to TI as observed in thebipectinatacomplex. Copulatory wounding is suggested to occur in other allied species of theDrosophila melanogasterspecies group, includingD. melanogaster. Ubiquitous sexual conflicts over mating may have led to the evolution of novel intromittent organs for insemination.