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

Table 1. Diagnostic characters separating species of Hydrobiomorpha. Fractions given for the mesotibial setigerous furrow indicate its relative length with respect to total mesotibial length; proportions of the glabrous area of the last abdominal ventrite correspond to the relative length of the glabrous patch with respect to the total length of the fifth abdominal ventrite.

Species	L (in mm)	Mesotibial furrow ( ♂)	Glabrous area of last abdominal ventrite ♂	Glabrous area of last abdominal ventrite ♀	Prosternal keel (shape and extension)	Metaventral keel (extent)	Modification of male claws
H. bachmanni sp. nov.	♂: 15.5–19.0	present (~ 1 / 3)	~ 2 / 5	~ 2 / 5	slightly concave; short	short, not reaching first abdominal ventrite	claws robust, proximal tooth pointed / blunt
	♀: 16.5–20.5
H. corumbaensis	♂: 15.5–17.5	absent	~ 1 / 4 – 1 / 3	absent	nearly straight; short	short, not reaching first abdominal ventrite	claws dissimilar; posterior metatarsal claw expanded
	♀: 15.5–18.6
H. iguazu	♂: 22.6	present (~ 1 / 4)	~ 3 / 4	~ 2 / 3	nearly straight; moderately long	long, reaching mid-length of first abdominal ventrite	claws robust, proximal tooth conspicuous
	♀: 21.0
H. irina irina	♂: 14.2–16.0	absent	<1 / 4	≤ 1 / 5	nearly straight; short	very long, reaching or slightly surpassing posterior margin of first abdominal ventrite	claws slender, proximal tooth long and hooked
	♀: 14.5–17.2
H. longa	♂: 14.0–15.3	absent	~ 1 / 3	absent	nearly straight; moderately long	short, not reaching first abdominal ventrite	claws modified; metatarsal claws angularly expanded
	♀: 14.8–16.6
H. rudesculpta	♂: 16.3–18.8	absent	very short, broad	absent	strongly oblique; long	moderately long, not reaching mid-length of first abdominal ventrite	claws strongly modified, proximal tooth enormous
	♀: 17.2–20.3
H. spinosa	♂: 13.7–17.9	present (~ 1 / 2 to 2 / 3)	<1 / 5 (often ~ 1 / 10)	absent	variable; generally long	very long, reaching or surpassing posterior margin of first abdominal ventrite	claws elongate, proximal tooth long and blunt
	♀: 14.0–20.5
H. utiariti	♂: 22.0	present (~ 1 / 2)	~ 2 / 3	<1 / 2	straight; short	long, reaching mid-length of first abdominal ventrite	claws robust, proximal tooth spatulate
	♀: 21.0–22.5