Hydrochus lobissimus, Perkins, 2020

Perkins, Philip D., 2020, Taxonomy of Ecuadorian water beetles in the genus Hydrochus Leach, 1817 (Coleoptera: Hydrochidae), Zootaxa 4790 (2), pp. 358-374 : 365

Hydrochus lobissimus , new species

Figs. 1 , 5

Type Material. Holotype (male): “ ECUADOR: Napo Limoncocha , 11 June 1977, P. J. Spangler & D. R. Givens #115” ( NMNH) . Paratypes (17): Same data as holotype (4 NMNH) ; Napo, Estacion Cientifica Yasuni , elev. 215 m (0°40’28’’S, 76°38’50’’W), 5-10.ix.1999, leg. E. G. Riley (3 TAMU) ; Limoncocha , (1°33’S, 75°35’W), 3.vi.1977, leg. W. E. Steiner (1 NMNH) ; same locality, 14.vi.1977, leg. W. E. Steiner (1 NMNH) ; same locality, 15.vi.1977, leg. W. E. Steiner (1 NMNH) ; Limoncocha, on Rio Napo, elev. 300 m, 10.iv.1974, leg. Boyce A. Drummond, III (6 NMNH) ; same locality, 23.iv.1974, leg. Boyce A. Drummond, III (1 NMNH) ; Santa Cecilia , (0°2’N, 76°58’W), 25-31.iii.1969, leg. P. & P. Spangler (1 NMNH) .

Differential Diagnosis. Among known Ecuadorian species, differentiated from all by the deep cervical groove behind the eyes. This species is a member of the H. collaris group (sensu Perkins 2019c); differentiated from the three other species in the group ( H. collaris Perkins , H. conjunctus Perkins , and H. purpureus Knisch ) by the larger and more closely spaced elytral punctures, the smaller body size (ca. 2.93 vs. 3.33-3.80 mm), and the male genitalia ( Fig. 5 ; described below).

Description. Habitus as illustrated ( Fig. 5 ). Size: holotype (length/width, mm): body (length to elytral apices) 2.93/1.10; head width 0.71; pronotum l/w 0.71/0.63; PA 0.61; PB 0.54; elytra 1.83/1.10. Body size moderate (ca. 2.93 mm). Dorsum grey to brown, with bronze or greenish, strong, iridescence, elytra with black spots. Punctation on elytra ca. 2-3x that of pronotum. Elytra interstriae ca. 0.5-1x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th well raised, rather elongate, ca. eight punctures in row on each side.

Head with deep curving cervical groove from side to side behind eyes, groove punctate, cervical area behind groove impunctate, shining.

Pronotum longer than wide (as ca. 71/63), widest at anterior margin, narrowed at base, sides very slightly arcuate, smooth; anterior margin markedly arcuate, fitting into cervical groove; depressions, especially anterior, deep, slightly more densely punctate than reliefs between depressions.

Elytra with spaces between strial punctures ca. 0.5–1x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with distinct angulation, impunctate area of apices rather large.

Ventral characters: Mentum coarsely punctate, with median fovea. Submentum with two foveae. Legs dark brown.

Male genitalia ( Fig. 5 ) general characters: genitalia slender; parameres laterally expanded apically in dorsal/ ventral views, tips wider in dorsal/ventral views than lateral view, extending very slightly beyond distal end of aedeagus, each paramere with very distinct pwsa slightly before midlength; basal piece shorter than parameres, lateral margins parallel for most of length, orifice strongly sclerotized, in lateral view hooking toward dorsad; aedeagus distal to adbl narrow in dorsal/ventral views, slightly wider at midlength than at distal end of adbl, tapering apically, lateral margins narrowly sclerotized in distal 1/2, in lateral view with proximal ½ of avm emarginate.

Dorsal surface: adtl lacking; pdmm approximating alm; adbl very large, widest part of aedeagus, much wider than paramere area adjacent to adbl.

Ventral surface: pvmm basally very narrowly separated, overlapping alm.

Etymology. Named in reference to the very large aedeagus dorsal basal lobe.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 5. Hydrochus lobissimus n. sp., habitus and male genitalia of holotype.