Evolution of a hyper-complex intromittent organ in rove beetles – the endophallus of Xantholinini (Staphylinidae: Coleoptera)

Studies on the functional morphology and evolution of genitalia have been crucial to understanding sexual traits in speciation, reproductive isolation and sexual selection in Coleoptera and insects in general. However, the focus of investigation of the intromittent organ of beetles was largely confined to the sclerotized elements of the aedeagus, whereas the membranous structures of the endophallus (=internal sac) have often not been adequately...