Hydrochus tripartitus, Perkins, 2020

Perkins, Philip D., 2020, Taxonomy of Peruvian water beetles in the genus Hydrochus Leach, 1817 (Coleoptera: Hydrochidae), Zootaxa 4868 (1), pp. 61-89: 83

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Hydrochus tripartitus

new species

Hydrochus tripartitus   , new species

Figs. 1 View FIGURE 1 , 15 View FIGURE 15

Type Material. Holotype (male): “ PERU: Madre de Dios; Rio Tambopata Res ; 30 air km SW Pto. Maldonado, 290 m, 26–30 xi 1979, J. B. Heppner, subtropical moist forest” ( NMNH)   . Paratypes (17): Peru: Same data as holotype (3 NMNH)   ; Madre de Dios, Rio Tambopata Res ; 30 air km SW Pto. Maldonado, elev. 290 m (13°0’S, 69°33’W), 6–10.xi.1979, leg. J. B. Heppner (1 NMNH) GoogleMaps   ; same locality, 11–15.xi.1979, leg. J. B. Heppner (2 NMNH) GoogleMaps   ; same locality, 16–20.xi.1979, leg. J. B. Heppner (7 NMNH) GoogleMaps   ; same locality, 21–25.xi.1979, leg. J. B. Heppner (4 NMNH) GoogleMaps   .

Differential Diagnosis. Among Peruvian species, recognized by the combination of small size (ca. 1.76–2.50 mm), the brown to black dorsum, the sub-oval body shape, the densely punctate pronotum, with deep depressions, the elytra with sutural and intervals 3, 5, 7, and 9 costate, and the male genitalia ( Fig. 15 View FIGURE 15 ; described below).

Description. Habitus as illustrated ( Fig. 15 View FIGURE 15 ). Size: holotype (length/width, mm): body (length to elytral apices) 1.76/0.72; head width 0.47; pronotum l/w 0.39/0.45; PA 0.43; PB 0.41; elytra 1.11/0.72. Body size small (ca. 1.76–2.30 mm). Dorsum dark brown to black, with slight to moderately strong iridescence, elytra without black spots. Legs brown, lateral margin of mesotibiae with row of spines. Head with frons medially slightly tumid, with longitudinal punctate groove on each side of tumidity. 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 not raised.

Pronotum densely punctate, slightly wider than long, widest slightly behind anterior margin, narrowed at base, sides weakly sinuate, smooth; anterior margin slightly bisinuate; depressions deep, slightly more densely punctate than reliefs between depressions.

Elytra with sutural and intervals 3, 5, 7, and 9 costate; 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 moderately coarsely and moderately densely punctate, with shallow median fovea. Submentum narrow, without foveae.

Male genitalia ( Fig. 15 View FIGURE 15 ) general characters: genitalia without parameres, basal piece elongate, arcuate in lateral view; distal piece arcuate in lateral view, terminating in three processes: short slender gonopore bearing flagellum, small hook-shaped process, and larger blade-like process.

Etymology. Named in reference to the three processes of the distal piece of the male genitalia.

Remarks. Refer to the remarks section of H. obliquus   , which also apply to H. tripartitus   n. sp.


Smithsonian Institution, National Museum of Natural History