Morphology and evolution of waterscorpion male genitalia (Heteroptera: Nepidae)

.  Male genitalia were comprehensively surveyed across the aquatic true bug family Nepidae. One hundred and forty‐one species in thirteen of fourteen genera and all five nepid tribes were dissected and studied. A family level description of waterscorpion male genitalia is provided that seeks to clarify the divisions of the phallus by comparison with the heteropteran male genitalia groundplan and with the phallus of the sister group of Nepidae, Belostomatidae. A comparative study of genitalia at the genus level revealed sixteen morphological groups that do not correspond precisely to the fourteen genera within the family. For example, there are distinct morphological groups within genera, e.g. two groups in Telmatotrephes and eight in Ranatra . By contrast, six genera, Borborophilus , Borborophyes , Laccotrephes , Montonepa , Nepella and Paranepa , form two groups. These morphological groups are the terminal units in a phylogenetic analysis based on twenty‐six male genital characters. The trees resulting from the analysis are distinctly different from Mahner's phylogenetic hypothesis for the family, which was based largely on nonreproductive traits. A hypothesis explaining the discordance of phylogenetic hypotheses generated from reproductive vs nonreproductive characters is presented.