Hydrochus amazonicus, 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 : 15-16

Hydrochus amazonicus , new species

Figs. 3 , 25 , 55

Type Material. Holotype (male): “ BRAZIL: Amazonas, Barcelos, Sr. Miranda, Comunidade Ucuqui, trilha, (0°48’.28’’N, 63°29’22.92’’W), 22–25.vii.2009, pool, leg. Pes, A. M. ” ( INPA) . Paratypes (173): Same data as holotype (23 INPA, MCZ, SEMC) ; Amazonas , Manicoré , Campos Amazônicos, Rio Branco -8.43761 -61.75055, 73 m, 5.vii.2018, small sandy puddle along river, leg. Short, BR 18-0705-03C (20 INPA, SEMC) ; Brazil , Amazonas , Novo Aripuanã, Campos Amazônicos, forested stream -8.63074 -61.42167, 130 m, 6.vii.2018, Small forested stream with lots of detritus, leg. Short, BR 18-0706-03A (19 INPA, SEMC) ; Barcelos , Igarape Ataiana, near Rio Negro, (1°0’38.05’’N, 62°52’16.98’’W), 10.viii.2009, leg. Ferreira-Jr N. (86 INPA, MCZ, SEMC) ; Sr. Miranda , Comunidade Ucuqui, igarapé 1, (0°47’54.27’’N, 63°29’11.55’’W), 22–24.vii.2009, leg. Pes, A. M. (20 INPA, MCZ) ; Sr. Miranda , rio Jauaperi, (0°48’2.77’’N, 63°29’1.32’’W), 26.vii.2009, leg. Ferreira-Jr N. (1 MCZ) ; same locality, 28.vii.2009, leg. Ferreira-Jr N. (5 MCZ) .

Differential Diagnosis. Similar in habitus to H. secretus ; differing therefrom in slightly smaller size, slightly denser and coarser dorsal punctation, and larger dorsal black spots. Reliable determinations will require dissection of the male genitalia ( Fig. 25 , described below), which also indicate a relationship with H. secretus .

Description. Size: holotype (length/width, mm): body (length to elytral apices) 3.88/1.38; head width 0.89; pronotum l/w 0.89/0.88; PA 0.86; PB 0.70; elytra 2.45/1.38. Habitus as illustrated ( Fig. 25 ). Dorsum brown to grey, with moderate to strong iridescence, elytra with black spots. Legs brown to testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2–5x that of pronotum. Elytra interstriae narrow walls to ca. 0.5x 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 and width ca. equal, widest at about anterior 1/3, narrowed at base, sides arcuate or very slightly sinuate, smooth; anterior margin arcuate or very slightly bisinuate; depressions moderately deep to deep, reliefs weakly raised, depressions and reliefs densely punctate.

Elytra with spaces between strial punctures narrow walls to ca. 0.5xpd; apices in dorsal view produced, apically truncate, slightly wider apically than subapically, in lateral view outer margin with strong angulation.

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

Male genitalia ( Fig. 25 ) general characters: genitalia small, moderately elongate, length ca. 4.3x greatest width, much wider in dorsal/ventral views than lateral (ratio ca. 2/1), basal piece much shorter than parameres (ratio ca. 5/8); paramere tips extending very slightly beyond aedeagus tip, medial margins beyond aedeagus tip rounded, plsa absent; in lateral view parameres almost straight, width ca. equal dorsal/ventral width, rounded apically; aedeagus wide, bifid apically, agw subapical, width gradually decreasing slightly to base, with distinctive alsm; basal piece in dorsal/ventral views narrowing from distal end to base, in lateral view sides nearly parallel, orifice strongly asymmetrical, margin sclerotized.

Dorsal surface: adtl absent; pdmm approximating alm in distal ½, overlapping alm in proximal 1/2; adbl moderately large, narrowly sclerotized.

Ventral surface: avtl absent; pvmm separation similar to pdmm, overlapping alm in proximal 1/2.

Etymology. Named in reference to the geographical distribution.

Figures

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

FIGURES 24–25. Habitus and male genitalia of holotypes. 24. Hydrochus accinctus n. sp. 25. Hydrochus amazonicus n. sp.

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