Taxonomy of Guatemalan water beetles in the genus Hydrochus (Coleoptera: Hydrochidae) Author Perkins, Philip D. text Acta Entomologica Musei Nationalis Pragae 2020 2020-04-23 60 1 291 301 journal article 21739 10.37520/aemnp.2020.016 6f4e1328-0bba-4f1c-aa66-4c1fe1fda040 1804-6487 3879760 45563A23-8582-4C53-81F3-591948E7A74D Hydrochus steineri sp. nov. ( Figs 1 , 7 ) Type material. HƟĿƟŦYPൾ:male ( NMNH ):‘ GUATEMALA : Peten ,Tikal, 28 June 1974 , W. E. Steinerʼ. Differential diagnosis. Among Guatemalan species, recognized by the combination of moderate size (ca. 3.29 mm ), the densely punctate pronotum with deep foveae, the elytra with strial punctures smaller than interstriae, and the male genitalia ( Fig. 7 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males. Description. Habitus as in Fig. 7 . Size (in mm): holotype : body (length to elytral apices / width) 3.29 / 1.18; head width 0.80; pronotum length / width 0.73 / 0.78; PA 0.76; PB 0.63; elytra 1.98/1.18. Body size moderate. Dorsum black, with moderately strong iridescence, elytra with non-iridescent black spots. Legs dark brown. Punctation on elytra ca. 2–4× that of pronotum. Elytra interstriae ca. 1.0–1.5× strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Callus on usual area of 5 th interstria large, strongly raised. Pronotum length slightly less than width, widest just behind anterior angles, narrowed at base, sides sinuate, smooth; anterior margin bisinuate; depressions deep, reliefs moderately sharply raised, depressions more densely punctate than reliefs. Elytra with spaces between strial punctures ca. 1× their diameter; 4 th interseries raised in area anterior to callus of 5 th ; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with weak angulation. Male genitalia ( Fig. 7 ). General characters: paramere tips slightly widened, distal ends pointed, lateral margins arcuate, medial margins of tips emarginate between angulation and distal end, and well separated from lateral margins of aedeagus, distal end of tips extending slightly beyond aedeagus, in lateral view tips narrow, sharply pointed; parameres in lateral view markedly sinuate; parameres with distinct pwsa at ca. proximal third; aedeagus moderately narrow in both dorsal/ventral and lateral views, agw at ca. mid-length, from which point markedly tapering to sharp distal end, with narrowly sclerotized lateral margins; basal piece much shorter than parameres, slightly wider in lateral than dorsal/ventral views, with rim of orifice moderately sclerotized. Fig. 8 Hydrochus lectotype labels.A – H. obscurus Sharp, 1882 ; B – H. debilis Sharp, 1882 . Dorsal surface: adtl located slightly distal to midlength of aedeagus; pdmm narrowly overlapping alm at base; adbl large. Ventral surface: pvmm very slightly overlapping alm at base. Etymology. Named in honor of Warren E. Steiner, longtime friend and colleague, who has collected many new species of Neotropical Hydrochus , including the only known specimen of this species.