Hydrochus quinarius, 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 : 33

Hydrochus quinarius , new species

Figs. 3 , 32 , 57

Type Material. Holotype (male): “ BRAZIL: Para , Belem, VII-9-10-1969, P. & P. Spangler ” ( NMNH).

Differential Diagnosis. Among Brazilian species, recognized by the combination of small size (ca. 2.41 mm), the pronotum with very shallow impressions, the pronotum with dense and rather uniformly distributed punctuation, the pronotal shape, the large black spots on the elytra, and the male genitalia ( Fig. 32 ; described below). Differentiation from other similarly small sized species with similarly shaped pronotum will require dissection of males.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.41/0.84; head width 0.60; pronotum l/w 0.54/0.54; PA 0.54; PB 0.45; elytra 1.53/0.84. Habitus as illustrated ( Fig. 32 ). Body size small (ca. 2.41 mm). Dorsum brown (holotype is teneral), elytra with several large black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2–3x that of pronotum. Elytra interstriae ca. 0.5x strial puncture diameter, or less. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th very weakly raised.

Pronotum slightly wider than long (ratio ca. 31/30), widest at anterior margin, narrowed at base, sides straight, smooth; anterior margin arcuate or very slightly bisinuate; depressions very shallow; punctation dense, quite uniform over pronotum

Elytra with spaces between strial punctures ca. 0.5–1x their diameter; apices rather sharply separately rounded in dorsal view, in lateral view outer margin with slight angulation.

Ventral characters: Mentum punctate, with deep central depression; submentum with two wide, deep, nearly confluent foveae.

Male genitalia ( Fig. 32 ) general characters: genitalia narrow, elongate, length ca. 5x greatest width, basal piece much shorter than parameres (ratio ca. 1/3); paramere tips extending well beyond aedeagus tip, tips lobate and widely separated from aedeagus, plsa absent; in lateral view parameres very narrow, widened slightly subapically, sharply pointed apically; pseudoparameres large, long, ca. ¾ length of parameres, rather wide, with very sparse reticulation; aedeagus narrow, in dorsal/ventral views decreasing in width from agw, at apex, to adbl; basal piece in dorsal/ventral views decreasing in width from distal end. to orifice, in lateral view very slightly arcuate, dorsal surface more arcuate than ventral, maximum width in dorsal/ventral views slightly greater than lateral width, orifice asymmetrical.

Dorsal surface: adtl subapical, very faint; pdmm widely separated from alm, except underneath lateral margin of adbl; adbl small, width much smaller than agw.

Ventral surface: avtl not apparent; pvmm same as pdmm.

Etymology. Named in reference to the five distal pieces of the male genitalia: aedeagus, 2 parameres, 2 pseudoparameres.

Figures

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

FIGURES 32–33. Habitus and male genitalia of holotypes. 32. Hydrochus quinarius n. sp. 33. Hydrochus baloghi Makhan.

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