Hydrochus forcipuloides, 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 : 26

Hydrochus forcipuloides , new species

Figs. 3 , 37 , 57

Type Material. Holotype (male): “ BRAZIL: Amazonas , Barcelos, Igarapé Serrinha, (0°24’33.88’’N,63°23’17.16’’), 1.viii.2009, pond, leg. Ferreira-Jr N.” ( INPA) . Paratypes (3): Same data as holotype (2 INPA); Nova Olinda do Norte, Lago Uruçanga, (3°56’27.17’’S, 59°3’50.56’’), 9.iv.2017, leg. Benetti, C.J.; Jorge, G.; Gusmão, G. (1 INPA) .

Differential Diagnosis. Among Brazilian species, recognized by the combination of small size (ca. 1.78 mm), the black color, the pronotum with very shallow impressions and rather uniform punctuation, the pronotal shape, and the male genitalia ( Fig. 37 ; 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) 1.78/0.69; head width 0.48; pronotum l/w 0.43/0.48; PA 0.48; PB 0.36; elytra 1.13/0.69. Habitus as illustrated ( Fig. 37 ). Dorsum dark brown to black, without iridescence, elytra without black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2–4x that of pronotum. Elytra interstriae ca. 0.5x strial puncture diameter, or less. Interstria 9 th slightly more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th very weakly raised, if at all.

Pronotum slightly wider than long (ratio ca. 26/23), widest at anterior margin, markedly narrowed at base, sides straight, smooth; anterior margin bisinuate; lateral and anterior margins with row of short setae; depressions very shallow; punctation quite uniform over pronotum

Elytra with spaces between strial punctures ca. 0.5x their diameter, to narrow ridges; some interstriae zig-zag; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with slight angulation; last puncture of each of first four series larger than others in series, translucent; ca. six last punctures of lateral most series larger than others, translucent.

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

Male genitalia ( Fig. 37 ) general characters: genitalia small, very narrow in distal 1/3, length ca. 6x greatest width, basal piece shorter than parameres (ratio ca. 5/7); paramere tips extending very slightly beyond aedeagus tip, plsa absent; parameres in dorsal/ventral views very narrow in distal ½, apically pointed and tips contiguous; in lateral view parameres narrower than aedeagus, tips arcuate toward ventrad; aedeagus comparatively wide at agw, at ca. midlength; basal piece in dorsal/ventral views widening from orifice to distal end, in lateral view arcuate, orifice very asymmetrical.

Dorsal surface: adtl not apparent; pdmm approximating alm; adbl small, ca. ½ to 1/3 agw.

Ventral surface: avtl at ca. midlength of aedeagus, margin delimiting large gp; pvmm approximating alm over distal ¾, slightly overlapping alm in proximal 1/4.

Etymology. Named in reference to some similarities of the male genitalia to that of H. forcipulus .

Figures

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

FIGURES 36–37. Habitus and male genitalia of holotypes. 36. Hydrochus forcipulus n. sp. 37. Hydrochus forcipuloides n. sp.

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