Traumatic mating by hand saw-like spines on the internal sac in Pyrrhalta maculicollis (Coleoptera, chrysomelidae, galerucinae)

Morphology of the aedeagus and vagina of Pyrrhalta maculicollis and its closely related species were investigated. The internal sac of P. maculicollis bears hand saw-like spines, which are arranged in a row. Healing wounds were found on the vagina of this species, whose females were collected in the field during a reproductive season. However, the number of the wounds is low in comparison to the number of the spines. In addition, males of P. tibialis bear one spinous sclerite on the internal sac, but the female of this species show no wounds on the vagina. The vaginal wall is thicker in P. maculicollis and P. tibialis in comparison to other studied species, whose males bear no spinous sclerite. This thickening in P. maculicollis is likely a counter-adaptation to wound infliction. Pyrrhalta maculicollis has a narrow internal sac in comparison to that of other Pyrrhalta species. Narrow internal sacs with spines can be potentially disadvantageous because their movement during copulation likely enhances the risk of self–infliction. Males of Pyrrhalta species have tiny membranous projections densely covering the internal sac surface, and it is hypothesized that they prevent damaging their own internal sac during everting and withdrawing the internal sac with the spines.