Key to the species of subgenus Hydaticus (Prodaticus) of the Neotropical Region 1. Elytron with a transverse and subbasal yellowish fascia (Fig. 1. Tbf)............................................. 2 - Elytron without a transverse and subbasal yellowish fascia (Fig. 2A)............................................. 5 2. Pronotum yellowish with a black band on anterior and posterior margin (Fig. 1, Abb, Pbb)............................ 4 - Pronotum black with broad yellowish lateral margins (Fig. 2B)................................................. 3 3. Elytron with basal fasciae confluent with sublateral, longitudinal and yellowish stripes; elytron without a subtriangular, postmedial and broad spot.......................................................................... H. devexus - Elytron usually with basal fasciae not confluent with sublateral, longitudinal and yellowish stripes; elytron with a subtriangular, postmedial and broad spot (Fig. 2B)............................................................... H. lateralis 4. TL 11.4–12.6 mm; pronotum with basal black band narrowly extended to anterior margin; elytron without sublateral yellow stripes, and with a large lateral spot just behind middle; apical third largely irrorated; protarsomere I with a series of spines across the dorsal surface; metatibia with bifid setae not parallel to dorsal margin on posterior surface (Fig. 2C).................................................................................................... H. subfasciatus - TL 9.6–10.4 mm; pronotum with basal black band not extended; elytron with sublateral and lateral yellow stripes, and without lateral spots; apical third largely rufous (Fig. 3D); protarsomere I without a series of spines across the dorsal surface; metatibia with bifid setae parallel to dorsal margin on posterior surface....................................... H. xanthomelas 5. Pronotum black with yellowish lateral margins (Fig. 2A)...................................................... 6 - Pronotum yellowish with a black band on anterior and posterior margin (Fig. 1, Abb, Pbb)............................ 7 6. Elytron with lateral, longitudinal and yellowish stripes, and without a subtriangular, postmedial and broad spot.. H. tuyuensis - Elytron without lateral, longitudinal and yellowish stripes, and with a subtriangular, postmedial and broad spot (Fig. 2A)...................................................................................... H. panguana sp. nov. 7. Protarsus without accessory medial spinous setae on dorsal surface of basal tarsomere of male; elytron without lateral yellow stripes..................................................................................... H. fractivittis - Protarsus with accessory medial spinous setae on dorsal surface of basal tarsomere of male; elytron with lateral yellow stripes (Fig. 1, Ls)........................................................................................... 8 8. Distribution: Colombia, Ecuador, Brazil, Paraguay and Argentina median lobe of aedeagus rounded apically in lateral view... ................................................................................................... 9 - Distribution: USA, Central America and West Indies; median lobe of aedeagus angulate or truncated apically in lateral view. .................................................................................................. 10 9. TL 10.8–12.5 mm; epipenite with apex rounded; median lobe of aedeagus in apical third greatly widened and rounded in dorsal view.................................................................................. H. inexspectatus - TL 13.0– 13.6 mm; epipenite with apex acute; median lobe of aedeagus in apical third subparallel and slightly rounded in dorsal view....................................................................................... H. palliatus 10. Median lobe of aedeagus angulate at apex in lateral view; each elytron with a definite and regular submarginal yellow stripe, more or less recurved at the base, without inward extensions; posterior black band of pronotum usually restricted to basal third; anterior disc of metatibiae generally with more than 10 large spines.................................. H. bimarginatus - Median lobe of aedeagus truncate apically in lateral view; each elytron with a submarginal stripe usually broad, sometimes with inward extensions (Fig. 3C); posterior black band of pronotum often extended to or almost to anterior margin; anterior disc of metatibiae generally with less than 10 large spines.................................................... H. rimosus

Published as part of Megna, Yoandri S., Balke, Michael, Apenborn, Rico & Hendrich, Lars, 2019, A review of Peruvian diving beetles of the genus Hydaticus Leach, 1817, with description of Hydaticus (Prodaticus) panguana sp. nov. and notes on other Neotropical species (Coleoptera: Dytiscidae), pp. 113-130 in Zootaxa 4615 (1) on pages 127-128, DOI: 10.11646/zootaxa.4615.1.5, http://zenodo.org/record/3995398