Hydrochus pronotulus, Perkins, 2021

Perkins, Philip D., 2021, Taxonomy of water beetles in the genus Hydrochus Leach, 1817, from Bolivia, Brazil and Paraguay (Coleoptera: Hydrochidae), Zootaxa 4994 (1), pp. 1-93 : 32

Hydrochus pronotulus , new species

Figs. 3 , 18 , 55

Type Material. Holotype (male): Brazil: Goias, “20 kil N. Sao Joao da Alianca , Go., Brazil, May 1 1956, F. S. Truxal ” ( NHMLAC).

Differential Diagnosis. Among Brazilian species, recognized by the combination of moderate size (ca. 3.44 mm), the black dorsal color, the small pronotum compared to the size of the elytra, the deep pronotal depressions, and the male genitalia ( Fig. 18 ; described below).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 3.44/1.27; head width 0.80; pronotum l/w 0.71/0.75; PA 0.75; PB 0.63; elytra 2.24/1.27. Habitus as illustrated ( Fig. 18 ). Body size moderate (ca. 3.44 mm). Dorsum black, with slight or no iridescence, elytra without black spots. Legs brown to testaceous, with tibiofemoral joints darker. 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 small, ca. 3 punctures on each side. Another, very small callus on 7 th, located slightly anterior to callus on 5 th.

Pronotum very slightly wider than long (ratio ca. 42/40), widest at anterior margin, narrowed at base, sides sinuate, smooth; anterior margin slightly bisinuate; depressions moderately deep, punctation rather uniform over pronotum.

Elytra with spaces between strial punctures narrow walls to ca. 0.5x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin without angulation.

Ventral characters: Mentum punctate, with central depression; submentum with two small foveae.

Male genitalia ( Fig. 18 ) general characters: genitalia moderately elongate, length ca. 4.8x greatest width, basal piece shorter than parameres (ratio ca. 1/1.5); parameres in dorsal/ventral views very narrow; paramere tips and aedeagus tip at same level, paramere tips arcing toward midline, tips widely separated, plsa absent, lateral margins of tips arcuate; in lateral view parameres narrow, very slightly sinuate, apex rounded; pseudoparameres wide in proximal 2/3, much narrower and tapering to pointed apex in distal 1/3, where medial margin with serrations; aedeagus in dorsal/ventral views very wide in distal 2/3, oval, much narrower in proximal 1/3, agw subapical; basal piece in dorsal/ventral views tapering from distal end to base, in lateral view slightly arcuate, greatest width in dorsal/ventral views greater than lateral width, orifice large, very slightly asymmetrical.

Dorsal surface: adtl at ca. proximal 1/3; pdmm widely separated from alm; adbl small.

Ventral surface: avtl not apparent; pvmm similar to pdmm except at tips where parameres slightly wider.

Etymology. Named in reference to the small pronotum, compared to the size of the elytra.

Figures

FIGURE 3. Dorsal habitus of Hydrochus species in study area.

FIGURES 18–19. Habitus and male genitalia of holotypes. 18. Hydrochus pronotulus n. sp. 19. Hydrochus velatus n. sp.

FIGURES 55–56. Geographical distributions. 55. Endemics and near endemics. 56. H. bicarinatus and H. merkli.