Hydrochus distinctus, 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 : 25

Hydrochus distinctus , new species

Figs. 2 , 6 , 57

Type Material. Holotype (male): “ Brazil: Distrito Federal , Estacao Florestal, Cabeca do Veado, 1100 m, 23–27 Oct.1971, E.G., I & E.A. Munroe” ( NMNH).

Differential Diagnosis. Among Brazilian species, recognized by the combination of large size (ca. 5.00 mm), the dorsal contrasting colors and sheen, dorsum with head and pronotum dull grey, elytra black and shiny, except each elytron with six dull grey, partially elevated interseries, and the male genitalia ( Fig. 6 ; described below).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 4.98/1.65; head width 1.09; pronotum l/w 1.09/1.07; PA 1.07; PB 0.91; elytra 3.26/1.65. Habitus as illustrated ( Fig. 6 ). Body size large (ca. 5.00 mm). Dorsum with head and pronotum dull grey, elytra black and shiny, except each elytron with six dull grey, partially elevated interseries; with slight iridescence; elytra without black spots. Legs testaceous to brownish orange, with tibiofemoral joints darker. Punctation on elytra ca. 6–8x that of pronotum. Elytra interstriae ca. 0.5–1.5x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th well raised, short, only ca. 4 punctures on each side. Each elytron also with six long raised interstriae: 3 rd, from base to ca. ¼; 4 th, from ca midlength to callus on 5 th; 5 th, from near base to ca. midlength; 7 th, from base to ca. ¼; 8 th, at humeral umbo; 9 th, for entire length. All of these areas grey to silver grey, dull and contrasting with black shiny surrounding area.

Pronotum only very slightly wider than long (ratio ca. 30/29), widest at anterior margin, narrowed at base, sides sinuate, smooth; anterior margin slightly bisinuate, and with row of short setae; depressions deep to moderately deep; punctation rather uniform over pronotum.

Elytra with spaces between strial punctures narrow ridges to ca. 0.5x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with angulation.

Ventral characters: Mentum and submentum densely, coarsely punctate; mentum with central depression; submentum with two foveae.

Male genitalia ( Fig. 6 ) general characters: genitalia large, elongate, length ca. 5x greatest width, basal piece very slightly longer than parameres; paramere tips extending well beyond aedeagus tip, medial margins beyond aedeagus tip parallel in distal part, then diverging, plsa moderately large, lateral margins between plsa and apex arcuate; in lateral view parameres almost straight, sharply pointed apically; aedeagus moderately wide, agw at about midlength, becoming narrower in basal 1/3; basal piece in dorsal/ventral views nearly parallel-sided, wider in dorsal/ventral views than lateral view, in lateral view very slightly arcuate, orifice slightly asymmetrical, margin strongly sclerotized.

Dorsal surface: adtl not apparent; pdmm well separated, overlapping alm in distal 2/3 of aedeagus, then approximating alm; adbl large, angulate laterally.

Ventral surface: avtl at ca. proximal ¼, margin delimiting large gp; pvmm more widely separated than pdmm, approximating alm.

Etymology. Named in reference to the pleasingly contrasting components of the dorsal sculpture and color.

Figures

FIGURE 2. Dorsal habitus of Hydrochus species in study area.

FIGURES 6–7. Habitus and male genitalia of holotypes. 6. Hydrochus distinctus n. sp. 7. Hydrochus triangularis n. sp.

FIGURES 57–58. Geographical distributions. 57. Endemics and near endemics. 58. H. bituberculatus.