Hydrochus usualis, 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 : 37-38

Hydrochus usualis , new species

Figs. 3 , 10 , 55

Type Material. Holotype (male): “ BRAZIL: Bahia, 15 Km. E. Itabuna, VII-3-1969, P. & P. Spangler ” ( NMNH) . Paratypes (37): Same data as holotype (19 NMNH) ; Brumado, Ibitira , ca. 22 km E on BR-30 (-14.23308 -41.90501), 556m, 27.ii.2018, roadside pond, mud substrate with marginal vegetation, leg. Benetti & Team, BR 18-0227-02A (3 INPA, SEMC) ; Guanambi , 10 km S on BR-122 (-14.31889 -42.78635), 530m, 27.ii.2018, densely vegetated pond, Benetti & Team, BR 18-0227-03A (3 INPA, SEMC) ; Mato Grosso, Cuiabá , (15°35’S, 56°5’W) collector unknown) (2 NMNH) ; Mato Grosso, Rio Bento Gomes (Pantanal); Flussabschnitt bei Periquito , (15°54’S, 56°33’W), 1.i.1993 – 30.xii.1994, leg. E. Stuhr (30) (5 NMW) ; Rio Grande do Norte, Ceara-Mirim , (5°38’S, 35°26’W), 6– 7.vii.1969, leg. P. & P. Spangler (5 NMNH) .

Differential Diagnosis. Among Brazilian species, recognized by the combination of moderate size (ca. 3.18 mm), the deep pronotal depressions, and the male genitalia ( Fig. 10 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 3.18/1.04; head width 0.73; pronotum l/w 0.68/0.70; PA 0.68; PB 0.62; elytra 2.01/1.04. Habitus as illustrated ( Fig. 10 ). Dorsum dark brown, with very slight iridescence, elytra with large medial black spots. Legs brown to testaceous, with tibiofemoral joints slightly 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. Callus on usual area of 5 th interstria moderately raised, moderately long.

Pronotum length slightly less than width, widest at about anterior 1/3, narrowed at base, sides sinuate, smooth; anterior margin slightly bisinuate; depressions rather deep, reliefs moderately raised, depressions densely punctate, reliefs very sparsely punctate.

Elytra with punctures large and deep on disc, producing zig-zag pattern of interstriae, spaces between strial punctures ca. 0.5–2xpd; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with angulation.

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

Male genitalia ( Fig. 10 ) general characters: genitalia elongate, length ca. 6x greatest width, basal piece very slightly longer than parameres; paramere tips extending very slightly beyond aedeagus tip, medial margins beyond aedeagus tip parallel, plsa very small, lateral margins between plsa and apex very slightly emarginate; in lateral view parameres almost straight, sharply pointed apically; aedeagus moderately narrow, almost parallel-sided for most of length; basal piece in dorsal/ventral views parallel-sided, in lateral view dorsal surface slightly more arcuate than ventral, width in dorsal/ventral and lateral views ca. equal, orifice slightly asymmetrical, margin sclerotized.

Dorsal surface: adtl very near distal end of aedeagus; pdmm widely separated near adtl, otherwise more narrowly separated, slightly overlapping alm; adbl moderately large, angulate laterally.

Ventral surface: avtl at ca. midlength of aedeagus; pvmm separation similar to pdmm, overlapping alm slightly; pseudoparameres very weakly sclerotized.

Etymology. Named in reference to the general shape of the adult and male genitalia.

Figures

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

FIGURES 10–11. Habitus and male genitalia of holotypes. 10. Hydrochus usualis n. sp. 11. Hydrochus merkli Makhan.

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