Revision of the genus Hydrobiomorpha Blackburn, 1888 (Coleoptera, Hydrophilidae) from Argentina, with the description of a new species and an updated identification key Author Urcola, Matías R. 0000-0002-1335-0072 Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento Biodiversidad y Biología Experimental, Laboratorio de Entomología, Buenos Aires, Argentina & CONICET-UBA, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Buenos Aires, Argentina Author Rodriguez, Georgina 0000-0002-0201-2932 Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento Biodiversidad y Biología Experimental, Laboratorio de Entomología, Buenos Aires, Argentina & CONICET-UBA, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Buenos Aires, Argentina Author Michat, Mariano C. 0000-0002-1962-7976 Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento Biodiversidad y Biología Experimental, Laboratorio de Entomología, Buenos Aires, Argentina & CONICET-UBA, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Buenos Aires, Argentina Author Torres, Patricia L. M. 0000-0002-6532-9347 Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento Biodiversidad y Biología Experimental, Laboratorio de Entomología, Buenos Aires, Argentina & CONICET-UBA, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Buenos Aires, Argentina text ZooKeys 2026 2026-08-11 1289 109 139 journal article 316041 10.3897/zookeys.1289.202453 f122728e-4c3e-42ec-a7d9-1458343f19f0 AA854D31-2E42-4639-B597-A4CA6A67DAFF Hydrobiomorpha iguazu Bachmann, 1988 Figs 1 C , 2 C , 3 C , 4 E , 4 F , 5 I – L Hydrobiomorpha iguazu : Contartese and Bachmann 1987 : fig. 3 (nomen nudum, distribution only). Hydrobiomorpha iguazu Bachmann, 1988: 9 , 15–16, fig. 31 A – H (original description; key to species of the Americas). Hydrobiomorpha iguazu : Bachmann et al. 2002 : 141 (female description). Type locality. Argentina : Misiones Province, Parque Nacional Iguazú [ 25°31'05"S , 54°08'00"W ]. Material examined. Argentina : • Misiones Province : Iguazú National Park [ 25°31'05"S , 54°08'00"W ], x.1980 , 1 ♂ ( holotype , MACN -En 2213 ) ; • same locality iv.2001 , PLM Torres and MC Michat leg., 1 ♀ ( MACN -En ) . Diagnosis. L : 22.6 mm (male holotype ), 21.0 mm (female). W : 10.6 mm (both sexes). Body shape (Figs 1 C , 2 C , 3 C ): subelliptical, slightly convex; elytral margin moderately reflexed on the posterior 2 / 3. Prosternal keel (Fig. 3 C ): moderately long, ventral margin nearly straight; posterior spine very short. Metaventral keel (Fig. 3 C ): slightly broadened, ending posteriorly in a short, laterally compressed, blunt tip, reaching approximately mid-length of first abdominal ventrite. Male: mesotibial setigerous furrow present, short, extending for ~ 1 / 4 of tibial length, with a short reddish setal brush (Table 1 ); fifth abdominal ventrite with a very large, subquadrate glabrous area, ~ 3 / 4 of its total length (Fig. 4 E ); protarsal claws unknown, not preserved in holotype (only known male); mesotarsal claws robust, with conspicuous proximal tooth; metatarsal claws robust, with conspicuous proximal tooth; genitalia: strongly sclerotized, median lobe subparallel, abruptly narrowed distally, apex bifurcate into two short sharp projections; accessory appendages of median lobe elongate, strongly sclerotized, with acute distal ends; parameres shorter than median lobe, broad in lateral view, narrowed distally and ending in projections, slightly curved towards midline (Fig. 5 I – L ). Female: fifth abdominal ventrite with a very large subtriangular glabrous area, ~ 2 / 3 of its total length (Fig. 4 F ). Distribution. Argentina : Misiones Province ( Bachmann 1988 ; Bachmann et al. 2002 ). Biology. The female was collected from a shallow pond of turbid water (~ 20 cm deep), near the entrance to the Macuco Trail in Iguazú National Park. No habitat data are available for the holotype . Remarks. The large size, 21.0– 22.6 mm and dark dorsal coloration resemble those of H. utinga Bachmann, 1988 , H. mucajai Bachmann, 1988 , H. solitaria Bachmann, 1988 , and H. praesumptapolita Bachmann, 1988 . The median lobe of the male genitalia resembles that of H. praesumptapolita (Bachmann, 1988) . The large bare area on the last abdominal ventrite, and the short setigerous furrow, of 1 / 4 the length of the mesotibiae of males, are distinctive; the above mentioned species have the furrow longer, half as long as the tibiae, and in H. mucajai it is absent.