Stenus (Hypostenus) trifurcatus Zhao, Cai & Zhou

Zhao, Cai-Yun, Cai, Wan-Zhi & Zhou, Hong-Zhang, 2008, Two new Stenus (Hypostenus) species from China (Coleoptera, Staphylinidae, Steninae), Zootaxa 1725, pp. 48-52 : 48-49

Stenus (Hypostenus) trifurcatus Zhao, Cai & Zhou , sp. n.

( Figs. 1–3 )

Type material. Holotype: CHINA: Hubei Prov.: male, Shennongjia, Jiucong, Wanjiagou (110°03'– 110°34'E, 31°21'– 31°36'N), 19 July 1998, 900 m, Zhou Hai-sheng collected. Paratype: CHINA: Hubei Prov.: male, same data as holotype, except 870 m, Luo Tian-hong collected.

Description. Body length: 4.1 mm.

Body black, pronotum and elytra reddish brown; antennae yellowish brown with five apical segments brown; maxillary palpi yellowish brown; clypeus and labrum reddish brown and both covered with sparse yellow pubescence, anterior margin of labrum yellow; legs yellowish brown except for knees dark.

Head wider than elytra (1.15:1), average distance between eyes 0.50 mm. Interocular area with a pair of shallow longitudinal furrows, area between furrows slightly convex and slightly narrower than each lateral portion; vertex with impuncate area along median longitudinal line, five times as long as puncture diameter; punctures on head larger than basal cross section of antennal segment III but smaller than its apical cross section, interstices with microsculpture and smaller than puncture diameter. Antenna long and reach posterior margin of pronotum when reflexed, three apical segments distinctly longer than wide. Paraglossae oval.

Pronotum longer than wide (1.11:1), widest near middle, sides strongly constricted after posterior 1/3; surface of pronotum uneven, with distinct longitudinal punctated furrow along median line which occupies 1/3 length of pronotum and gradually weakens forward and backward, punctures on pronotum coarse, larger than those on head but smaller than basal cross section of antennal segment II, interstices smooth and smaller than half of puncture diameter. Elytra (measured along suture) shorter than pronotum (0.77:1), as long as wide (0.80 mm), sides inflated, widest just before posterior margin. Each elytron without emargination in outer part of hind margin, but hind margin of both elytra combined form broad curve. Surface of elytra convex, with shallow humeral depression, and broad depression along suture which gradually becomes shallower and narrower posteriorly. Punctures on elytra slightly larger than basal cross section of antennal segment III, interstices smooth and larger than puncture diameter. Hind wings absent in all examined specimens.

Legs robust; metatarsi 1st segment longer than following two segments combined, 3rd and 4th bilobed, but lobes of 4th much longer.

Abdomen robust, 3rd segment with narrow paratergite, tergites and sternites of 4th–6th segments completely fused and only with slight trace of suture at base; 3rd–6th tergites with transverse impression at base; punctures on tergites distinct: on 3rd–6th tergites smaller than basal cross section of antennal segment III, interstices larger than puncture diameter; on 7th tergite slightly smaller than diameter of inner eye-facet, interstices larger than puncture diameter. Tergites covered with golden yellow pubescence, denser in lateral portions of tergites.

Male: 8th abdominal sternite with shallow apical emargination ( Fig. 3 ), 9th abdominal sternite with two strong apical teeth without secondary dentation on their outer sides ( Fig. 2 ). Aedeagus ( Fig. 1 ): median lobe broad, apex with medial acicular projection and small emargination on each side of the projection; parameres distinctly longer than median lobe, with sparse long hairs apically.

Female: Unknown.

Etymology. The species epithet is derived from Latin words tri- (three) and - furca (with tooth).

Remarks. This new species belongs to asyura group (for definition of this group see Naomi 1988). This is the first species of this group described from China. The new species can be easily distinguished from all Chinese species of subgenus Hypostenus by the presence of acicular projection and two emarginations in the apex of the median lobe. The new species is similar to several Japanese species, S. (H.) asyura Naomi, 1988 , S. (H.) santira Naomi, 1988 , S. (H.) basara Naomi, 1988 and S. (H.) daikoku Naomi, 2004 , but differs in having the apical part of the median lobe broader and the acicular projection of the apex longer.

Figures

FIGURES 1 – 8. Details of Stenus (H.) trifurcatus sp. n. (1 - 3) and S. (H.) cuneatus sp. n. (4 - 8). 1, 4 — aedeagus; 2, 5 — male sternite IX; 3, 6 — male sternite VIII; 7 — hooks of internal sac; 8 — spermatheca. Scale bars: 0.1 mm.