Hydrochus reticulatus, 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 : 34-35

Hydrochus reticulatus new species

Figs. 1 , 14 , 57

Type Material. Holotype (male): Brazil: Bahia, Morro do Chapéu, Cachoeira do Ferro Doido (-11.62779 - 41.00072), 890m, 24.ii.2018, margins of blackwater river on rock, leg. Benetti & Team, BR 18-0224-01A ( INPA) . Paratypes (6): Same data as holotype (4 INPA, SEMC) ; Minas Gerais, Monte Azul, Serra do Espinhaço, c. 7 Km E of Monte Azul (-15.17067 -42.80351), 970 m., 28.ii.2018, margins of forested stream, leg. Benetti & Team, BR 18- 0228-02A (2 INPA, SEMC) .

Differential Diagnosis. Among Brazilian species, recognized by the combination of moderate size (ca. 2.45 mm), the black dorsal color, the oval body form, the odd numbered elytral interstriae subcostate, the pronotum coarsely densely, rather uniformly punctate, with deep depressions, and the male genitalia ( Fig. 14 ; described below). Completely reliable determinations will include dissection of males.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.45/1.01; head width 0.64; pronotum l/w 0.55/0.65; PA 0.59; PB 0.51; elytra 1.63/1.01. Habitus as illustrated ( Fig. 14 ). Body size moderate (ca. 2.45 mm). Dorsum black, with very slight or no iridescence, elytra without black spots. Legs brown, with tibiofemoral joints darker. Punctation on elytra ca. 2–3x that of pronotum. Elytra interstriae ca. 0.5x strial puncture diameter; odd numbered interstriae subcostate. Usual area of callus on 5 th not raised.

Pronotum slightly wider than long (ratio ca. 35/29), widest slightly behind anterior margin, narrowed at base, sides weakly sinuate, denticulate; anterior margin arcuate; depressions deep; pronotum coarsely densely, rather uniformly punctate.

Elytra with spaces between strial punctures ca. 0.5x their diameter; apices conjointly rounded in dorsal view, in lateral view outer margin with slight angulation; lateral most row of punctures in groove.

Ventral characters: Mentum punctate, with central depression; submentum with two large, narrowly separated foveae.

Male genitalia ( Fig. 14 ) general characters: genitalia small, very narrow, elongate, length ca. 6x greatest width, basal piece shorter than parameres, as ca. 13/16; paramere tips extending very slightly beyond aedeagus tip, plsa absent; parameres in dorsal/ventral views very narrow, especially in distal 1/2; in lateral view parameres narrow, slightly arcuate toward ventrad, very sharply pointed apically; aedeagus moderately wide, agw at midlength, where aedeagus wider than parameres; basal piece in dorsal/ventral views widening very slightly from orifice to distal end, in lateral view slightly arcuate, much narrower than in dorsal/ventral views, orifice only very slightly asymmetrical.

Dorsal surface: adtl not apparent; pdmm approximating alm; adbl moderately large, angulate laterally, width less than agw; proximal ¾ of aedeagus with distinctive reticulate pattern.

Ventral surface: avtl not apparent; pvmm in distal ½ slightly overlapping alm, otherwise approximating alm.

Etymology. Named in reference to the reticulate dorsal surface of the aedeagus.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species in study area.

FIGURES 14–15. Habitus and male genitalia of holotypes. 14. Hydrochus reticulatus n. sp. 15. Hydrochus personatus n. sp.

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