Hydrochus colossus, 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 : 21

Hydrochus colossus , new species

Figs. 1 , 52 , 53

Type Material. Holotype (female): “ BRAZIL: Mato Grosso do Sul, Aquidauana (c. 27 km S) on MS-174 (- 20.72281, -55.69127); 225m; leg. Hamada and team; 27.vi.2018; seepage and debris nr. stream margin; BR18- 0627-01E” ( INPA).

Differential Diagnosis. A member of the H. spanglerorum species group, differentiated from the other members ( H. accinctus and H. colossus ) by the combination of large, robust, strongly sclerotized body (ca. 5.10 x 2.00 mm), the densely punctate dorsum, the relatively wide elytral interstriae. Refer to the diagnosis of H. accinctus for characteristics of the H. spanglerorum species group.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 5.07/2.00; head width 1.17; pronotum l/w 1.22/1.29; PA 1.12; PB 1.07; elytra 3.46/2.00. Habitus as illustrated ( Fig. 52 ). Very large (ca. 5.07 mm), elongate. Dorsum grey to black to very faint dull gold, with little iridescence; elytra with numerous black spots. Legs dark brown to black; all surfaces of femora densely coarsely punctate; tibiae with outer apical margin produced and bearing few short stout spines. Pronotum very densely, coarsely punctate. Elytral striae with deep round punctures; interstriae wider than striae.

Head densely, coarsely punctate; frons markedly raised in middle, with deep groove on each side of timidity, area between groove and eye also convex; frontoclypeal suture absent; clypeus disc convex.

Pronotum wider than long (L/W as ca. 1.22/1.29), widest at about distal 2/3; anterior margin bisinuate; narrowed at base; sides denticulate, sinuate; punctures on pronotum moderately sized, deep, very dense; depressions very deep, central depression margined laterally with rather sharp ridge.

Elytra with strial punctures very deep and ca. 2–3x those on pronotum; interstriae ca. 2x width of striae; 3 rd and 5 th interstriae raised, costate to subcostate, throughout length, not additionally raised at usual area of callus; 9 th interstria raised and overhanging 10 th; apices truncate, with submarginal row of large, elongate punctures.

Ventral characters: Mentum and submentum each with 2 foveae.

Female genital segments as illustrated ( Fig. 52 ).

Etymology. Named in reference to the very large body size.

Figures

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

FIGURE 52. Hydrochus colossus n. sp., habitus and female genital segments of holotype.

FIGURES 53–54. Geographical distributions. 53. H spanglerorum species group. 54. H collaris species group.