Trechus yak, Schmidt, 2009

Schmidt, Joachim, 2009, Taxonomic and biogeographical review of the genus Trechus Clairville, 1806, from the Tibetan Himalaya and the southern central Tibetan Plateau (Coleoptera: Carabidae: Trechini) 2178, Zootaxa 2178 (1), pp. 1-72 : 47-48

Trechus yak sp. n.

( Figs. 8 , 69, 76 )

Type material: Holotype male, with label data “ TIBET South Centr. 17–20.VI.07, Budha Vall. N of Yangpachem, ca. 30°10’56N 90°29’21E, 5000–5200 m ” ( BMNH).

Paratypes: 27 males, 8 females, with the same label data as holotype ( BMNH, CKAB, CSCHM, CWR, MNHN, SMNS) ; 19 males, 6 females, South Central Tibet, Budha Vall. N of Yangpachem, 5300–5600 m, ca. 30°11’07N 90°28’42E, 19.VI.2007 ( CSCHM) .

Description: Body length: 3.4–3.9 mm.

Colour: Dorsal surface shiny yellowish or light reddish brown, with head and distal 2/3 of elytra in most specimens shadowed. Antennae, palpi and legs yellowish brown; distal half of antennal segment III as well as antennal segments IV–XI on the whole darkened.

Microsculpture: Supraorbital area and disc of pronotum almost polished, with very faintly engraved meshes, only visible under high magnification (x100). More deeply engraved almost isodiametric meshes in frontal furrows of head and in pronotal basal depression. Slightly engraved slightly transverse meshes on disc of elytra (x60–x80).

Head: Rather stout, with eyes small and slightly protruding. Temples approximately 3/4 of length of eyes and strongly wrinkled to the neck. Frontal furrows not or slightly flattened at level of hind suborbital seta. Antennae stout, 2.5–3 antennomeres extend beyond the pronotal base. Antennomere III slightly longer than antennomere II, the latter slightly longer than antennomere IV.

Pronotum: Average sized, cordate, moderately transverse and strongly contracted towards base; proportions WP/LP = 1.22–1.26, WP/WPB = 1.28–1.32, WP/WH = 1.22–1.25, WE/WP = 1.60–1.64. Surface strongly convex. Sides concave anterad of hind angles; the latter moderately large, distinctly bent outwards, pointed. Marginal gutter narrow, not or slightly widened anterad of laterobasal depressions. Base rectilinear or slightly convex in middle, more strongly curved anteriorly at outer fifth; basal depressions usually smooth, in some specimens with fine wrinkles both sides of the middle of the pronotum.

Elytra: More slender oval, broadest at mid-length, with proportion WE/LE = 1.57–1.61. Surface strongly convex, not flattened on disc. Shoulders distinct but rounded. Striae punctate, first stria fully deep impressed, second, third, and mostly also fourth stria deeply impressed on disc but flattened at base and extreme apex, outer striae shallower but always present. Stria VIII slightly impressed from level of the fifth umbilicate pore backwards and more deeply impressed at levels of seventh and eighth pores. Recurrent elytral preapical sulcus connected with the end of the fifth or seventh stria. Intervals I–IV (-V) strongly convex. Preapical seta is located at the end of second stria and at the beginning of the last tenth of the elytra.

Legs: Moderately short.

Male genitalia: Aedeagal median lobe moderately short (LE/LA = 3.2–3.4), evenly curved towards apex. Basal bulb average. Terminal lamella short and slightly curved upwards. Sclerotized portion of internal sac consist of a prominent copulatory piece, which is more tube-like and evenly curved in lateral view, and more thorn-like in dorsal view. Parameres average.

Etymology: The specific name refers to the Yak ( Bos grunniens ), the most important domestic animal of the Tibetans, which is frequently grazing in the whole distributional area of the new Trechus species. Noun in apposition.

Identification: In external characters very similar to T. antonini Deuve, 1997 , but with shoulders broader, with outer elytral striae more deeply impressed, and with pronotal hind angles sharper and more distinctly protruding. Also very similar to T. religiosus sp. n., but body on average larger, and the pronotal base more strongly bent anteriorly towards hind angles. Moreover, T. yak sp. n. is easily distinguished from both the latter species by the prominent copulatory piece of the aedeagal internal sac.

Relationships: Unknown.

Distribution and geographical variation: Fig. 100 . This species was found along the upper Budha Valley of the south slope of the central Nyainqentanglha Shan Massif, north of Yangpachem. More populations where found approximately 40 km south west of Yangpachem along the uppermost Shogu Tshu Valley of western Nyainqentanglha Shan Massif. These populations differ in the pronotal shape and in the form of the male copulatory piece. Based on these morphological differences a distinct subspecies for the populations of the Shogu Tshu Valley is described below.

Habitat: Higher alpine zone; vertical distribution approximately 5000–5400 m. The nominotypical form was frequently found under big stones on humid, gently inclined slopes in southern and western exposition.

Figures

FIGURE 100. Map of Southern Central Tibet showing distribution of species of the Trechus antonini group (white circles). 1, T. antonini Deuve, 1997. 2, T. religiosus sp. n. 3, T. astrophilus sp. n. 4, T. budhaensis sp. n. 5, T. rarus sp. n. 6, T. yeti sp. n. 7, T. folwarcznyi Deuve, 1997. 8, T. yak yak ssp. n. 9, T. yak shogulaensis ssp. n. 10, T. tseringi sp. n. 11, T. singularis sp. n. 12, T. tsampa sp. n. 13, T. lama sp. n.

FIGURES 2–11. Pronotum. Fig. 2, Trechus thibetanus Jeannel, 1928, Lectotype. Fig. 3, T. dongulaensis sp. n., paratype, male. Fig. 4, T. namtsoensis sp. n., paratype, male. Fig. 5, T. eutrechoides eutrechoides Deuve, 1992, non-type male specimen from Lamna La. Fig. 6, T. glabratus sp. n., paratype, male. Fig. 7, T. korae sp. n., paratype, male. Fig. 8, T. yak yak ssp. n., paratype, male. Fig. 9, T. yak shogulaensis ssp. n., paratype, male. Fig. 10, T. rolwalingensis rolwalingensis ssp. n., paratype, male. Fig. 11, T. rolwalingensis daldunglana ssp. n., paratype, male.

FIGURES 65–80. Aedeagal median lobe with sclerotized portions of internal sac in lateral view (Figs. 65–71, 77–80; Figs. 65, 68–71, 79, 80 in addition with parameres) and in dorsal view (Figs. 72–76). Figs. 65, 74, Trechus astrophilus sp. n., paratype. Fig. 66, T. lama sp. n., paratype. Fig. 67, T. singularis sp. n., holotype. Fig. 68, T. tsampa sp. n., paratype. Figs. 69, 76, T. yak yak ssp. n., paratype. Figs. 70, 73, T. religiosus sp. n., paratype. Figs. 71, 72, T. chaklaensis sp. n., paratype. Fig. 75, T. yak shogulaensis ssp. n., paratype. Fig. 77, T. antonini sp. n., non-type specimen from Lhachen La (= locus typicus). Fig. 78, T. folwarcznyi Deuve, 1997, non-type specimen from Shogu La (= locus typicus). Fig. 79, T. rarus sp. n., holotype. Fig. 80, T. tseringi sp. n., paratype.