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 rudesculpta (d’Orchymont, 1939) Figs 1 F , 2 F , 3 F , 4 K , 4 L , 5 U – X , 6 O , 7 E , 7 I Neohydrophilus rudesculptus d’Orchymont, 1939 a: 376–378 (original description). Hydrobiomorpha rudesculpta : Mouchamps 1959 : 324 , 333. Hydrobiomorpha (Hydrobiomorpha) rudesculpta : Bachmann 1963 : 29 , 32, fig. 3 (key to Argentine species). [Neohydrophilus] rudesculptus : Döbler 1977 : 386 . Hydrobiomorpha rudesculpta : Contartese and Bachmann 1987 : fig. 2 (distribution only). Hydrobiomorpha rudesculpta : Bachmann 1988 : 8 , 45–46, fig. 30 A – H (redescription; key to species of the Americas). Type locality. Paraguay : Río Pilcomayo. Material examined. Argentina : • Chaco Province : Resistencia [ 27°27'05"S , 58°59'12"W ] [no date], JB Daguerre leg., 1 ♂ ( LEBA ) ; • San Bernardo [ 27°17'30"S , 60°42'30"W ], ii.1980 , OR Di Iorio leg., light trap , 1 ♂ and 2 ♀♀ ( LEBA ) . • Corrientes Province : Iberá lagoon , 28°32'46"S , 57°11'45"W , 7.xi.2019 , JI Urcola and G Rodriguez leg., light trap , 1 ♀ ( LEBA ) ; • Manantiales [ 29°21'26"S , 59°17'44"W ], ix.1960 , 1 ♀ ( LEBA ) . • Salta Province : Piquete [ 24°45'17"S , 64°28'08"W ], 18.i.1928 , A Bridarolli leg., 1 ♀ ( MACN -En ) . • Santa Fe Province : Chaco [likely refers to the biogeographic province] [no date], C Bruch leg., 1 ♂ ( MACN -En ) . • No locality data: [no date], A Breyer leg., 1 ♀ ( MACN -En ) . Diagnosis. L : 16.3–18.8 mm (males), 17.2–20.3 mm (females). W : 8.8–9.9 mm (males), 9.4–11.6 mm (females). Body shape (Figs 1 F , 2 F , 3 F ): broadly oval, widest slightly posterior to mid-length of elytra, strongly convex (subglobose); elytral margins not reflexed. Prosternal keel (Fig. 3 F ): strongly oblique, posterior spine very long. Metaventral keel (Fig. 3 F ): very short, posterior tip blunt, not reaching mid-length of first abdominal ventrite. Male: mesotibial setigerous furrow absent (Table 1 ; Fig. 7 E, I ); ventral inner face of mesotibia with a very dense distal patch of spinules; claws highly distinctive; protarsal claws with enormous spatulate proximal tooth on inner claw; mesotarsal claws with very large, rounded, oblique proximal tooth; metatarsal claws long, with large, rounded proximal tooth (Fig. 6 O ); fifth abdominal ventrite with small, wide, poorly delimited glabrous area (Fig. 4 K ); genitalia: median lobe very broad, largely membranous, apex with two large rounded lobes; accessory appendages of median lobe narrow in dorsal view, broad in lateral view, strongly sclerotized, distally bent at a right angle toward the midline, bearing an acute outwardly directed process at the point of inflection; parameres slightly shorter than median lobe, with a subdistal dorsal projection directed proximally and a complex basal lobe (Fig. 5 U – X ). Female: fifth abdominal ventrite without glabrous area (Fig. 4 L ). Distribution. Paraguay ( d’Orchymont 1939 a ; Mouchamps 1959 ; Bachmann 1963 , 1988 ), Argentina (provinces): Chaco ( Bachmann 1963 , 1988 ; this study), Corrientes ( Bachmann 1963 , 1988 ; Torres et al. 2012 ; this study), Entre Ríos ( Bachmann 1963 , 1988 ), Formosa ( Bachmann 1963 , 1988 ), Salta ( Bachmann 1963 , 1988 ), Santa Fe ( Bachmann 1963 ). Biology. To date, the biology of this species remains unknown; however, it is frequently collected using light traps ( Torres et al. 2012 ; this study). Remarks. Hydrobiomorpha rudesculpta is the most anatomically distinctive Argentine species of the genus, recognizable by its subglobose body shape, the spatulate proximal tooth of the anterior protarsal claw in males (Fig. 6 O ), and the distinctive structure of the male genitalia (Fig. 5 U – X ; see Diagnosis for details). No other species combines these characters.