Rhantus fengi, Zhao, Shuang, Jia, Fenglong & Balke, Michael, 2011

Zhao, Shuang, Jia, Fenglong & Balke, Michael, 2011, Rhantus fengi sp. n. from Xizang, China, and notes on Laccoporus nigritulus (Gschwendtner) (Coleoptera, Dytiscidae), ZooKeys 94, pp. 61-71 : 63-64

Rhantus fengi sp. n. Figs 1-8

Type locality:

China: Xizang, Mount Sejila, 29°37'N, 94°37'E.

Type material.

Holotype ♂ CHINA: Xizang, Mount Sejila, altitude 4200 m, 16.viii.2009, leg. Fenglong Jia [translation; labeled in Chinese] (SYSU); Paratypes (47 exs): 12 exs, same data as holotype (SYSU; 3 exs in CGC; 2 exs in ZSM); 4 exs same data as holotype but 12.viii.2009 (SYSU); 7 exs same data as holotype but 15.viii.2009 (SYSU); 4 exs same data as holotype but 17.viii.2009 (SYSU); 4 exs same data as holotype but 18.viii.2009 (SYSU); 3 exs same data as holotype but 13.-15.viii.2009 (SYSU); 2 exs Xizang, Bayi Town, Biological Study Base of SYSU, altitude 4200 m, vii.-ix.2009, leg. Shuai Jiang (SYSU); 4 exs Xizang, Mount Sejila, altitude 4100 m, vi.2009, leg. Shuang Zhao (SYSU).

Diagnosis.

General appearance of beetle rather dark, epipleuron black.

Description.

Body elongate-oval (Fig. 1).

Measurements.

Body length 13.2-14.1 mm, width 6.2-6.5 mm.

Colour.

Head black, with orange triangular mark on frons and contrasting yellow clypeus (Fig. 3). Scape and pedicel yellow, antennomeres 2-5 piceous with yellow base, antennomeres 6-11 piceous. Maxillary and labial palps piceous. Pronotum yellow to yellowish brown, with a wide transverse black medial maculation that not reaching anterior and posterior margin; anterior and posterior margins with black bands rather broad medially that become lighter laterally, sometimes becoming thin laterally, lateral margin black except anterior angle, near anterior and posterior margins usually with somewhat regular black spots. Elytra yellow to yellowish brown, disc with very dense black speckles giving elytra dark appearance; lateral margin, base of elytra and near suture with yellow band, suture black; epipleura black. Ventral surface and legs black (Fig. 2), trochanters with yellowish base, pro- and mesotarsal claws somewhat dark brown.

Surface sculpture.

Head with irregular polygonal meshes and fine punctation; meshes rather elongated and punctures coarser behind posterior margins of eyes; along inner face of eye with series of coarse setiferous punctures. Pronotum with irregular polygonal meshes and fine punctuation; along anterior and posterior margins with rows of coarse punctures, interrupted posteromedially; lateral portion distinctly depressed, without microreticulation, with broad rim (or border) reaching anterior angle; posterior angle broadly rounded. Elytra with irregular polygonal meshes and fine microreticulation best visible laterally and posteriorly (at 50 ×); each elytron with five rows of coarse setiferous punctures being somewhat irregular except in row 1 (sutural row) and very regular row immediately along lateral margin; elytral disc with similar meshes and fine punctures as on pronotum, mircroreticulation faint, hardly visible. Metaventrite ("metasternal wings") broad laterally. Metafemur without group of setae on posteroexternal angle. Pro- and mesotarsomeres with claws gently curved; outer protarsal claw slightly shorter than inner one (Fig. 5) and inner mesotarsal claw distinctly shorter than outer one; inner hindclaw twice as long as outer one. Abdominal ventrites 4 and 5 with a transverse rows of coarse setiferous punctures; ventrite 6 rugose with stronger punctures and setae laterally, more or less depressed and smooth posteromedially.

Male.

Abdominal ventrite 6 posteriorly emarginate, with fine wrinkles laterally. Pro- and mesotarsomeres 1-3 clearly expanded laterally, with four rows of stalked suction discs ventrally (Fig. 6). Number of discs per transverse row: 5 discs (on tarsomere 1) - 5 discs (second row on tarsomere 1) - 5 discs (on tarsomere 2) - 5 discs (on tarsomere 3). Parameres with dense and long setation, some setae distally trumpet-shaped (Fig. 7). Median lobe of aedeagus as in Fig. 8.

Female.

Abdominal ventrite 6 simply rounded posteriorly (Fig. 4), pro- and mesotarsomeres 1-3 not expanded laterally, without stalked suction discs.

Remarks.

The elytral sculpture of polygonal meshes and microreticulation as well as the parameres with some trumpet shaped setae, place this species in the Rhantus suturalis group ( Balke 1993). The species is well characterized by its black epipleura; this is shared only with the Bhutanese species Rhantus gogonensis Wewalka, 1975 (Fig. 9) which is only known from the female holotype (Bhutan: Sha Gogona; http://www.species-id.net/wiki/Rhantus_gogonensis). Rhantus fengi differs from the latter by the darker body, pronotum not narrower than the base of elytra; pronotum distinctly impressed laterally; head, pronotum and elytra with very dense fine punctures, and black tarsi and antenna.

Etymology.

The species is named in honour of Hsiao-Tang Feng, a pioneer in the Chinese Dytiscidae studies.

Habitat.

Collected from a branch of a small stream with fine sand on bottom. The water of the stream was about 10-15 cm deep and slowly flowing.