Numerous new material of the genus Motonerus Hansen, 1989 (Coleoptera: Hydrophilidae: Sphaeridiinae) was examined over the past decade, resulting in the discovery of several undescribed species as well as new distributional records for most of the previously described species. Three species are here described as new: Motonerus explanatus sp. nov. (Panama), M. inca sp. nov. (Venezuela, Ecuador, Peru, Bolivia) and M. sofiae sp. nov. (Peru). New country records are provided for M. depressus Fikáček & Short (new for Venezuela, Ecuador, Peru and Bolivia), M. hanseni Fikáček & Short (new for Panama) and M. problematicus Fikáček & Short (new for Panama). An updated identification key and distributional maps are provided for all species, along with complete occurrence data in a DarwinCore formatted file. Potential distribution of the genus is modeled using the maximum entropy approach. Wing morphology is examined in detail, which revealed most species are macropterous, with M. andersoni Fikáček & Short being brachypterous, and M. apterus Fikáček & Short, M. oosternoides Fikáček & Short, and M. explanatus sp. nov. micropterous. The third instar of the putative larva of M. obscurus Hansen is briefly described based on larvae collected in association with adults.

Dept of Entomology National Museum Cirkusová 1740 Praha 9 CZ 19300 Czech Republic Dept of Zoology Faculty of Science Charles Univ Vinicna 7 Praha 2 Czech Republic

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