The New World whirligig beetles of the genus Dineutus Macleay, 1825 (Coleoptera, Gyrinidae, Gyrininae, Dineutini)

All New World members of the whirligig beetle genus Dineutus Macleay, 1825 are treated. The New World Dineutus are found to be composed of 18 species and 6 subspecies: one species, Dineutus mexicanus Ochs, 1925, stat. n. is elevated from subspecies to species rank, and the subspecies D. carolinus mutchleri Ochs, 1925, syn. n. is synonymized here with the typical form. Lectotypes are designated for D. discolor Aube, 1838, D. metallicus Aube, 1838, D. solitarius Aube, 1838, D. analis Regimbart, 1883, and Gyrinus longimanus Olivier, 1795. Each taxonomic unit is provided with a taxonomic history, type locality, diagnosis, distribution, habitat information, and a discussion section. The aedeagus and male mesotarsal claws are illustrated, and dorsal and ventral habitus images of both sexes, for each species and subspecies are provided. General distribution maps are provided for all taxonimc units. A key to the genera of New World Gyrinidae, as well as all the New World Dineutus species is provided. General Dineutus anatomy as well as a clarification of homology and anatomical terms is included.