Tribasodites biyun Yin and Zhou, 2018

Yin, Zi-Wei & Zhou, Gu-Chun, 2018, Two new cavernicolous Pselaphinae (Coleoptera: Staphylinidae) from southern China, Zootaxa 4457 (4), pp. 589-594 : 592-594

Tribasodites biyun Yin and Zhou , new species

( Fig. 3 )

Type material (2 exs). Holotype: CHINA: ♂: ‘ China: Hunan, Shaoyang City, Chengbu Miao autonomous county, Leng-shui-ping Village , Biyun Cave , 26°20’33.84’’N, 110°19’45.39’’E, 473 m, 10.xi.2017, Gu-Chun Zhou leg. [湖 南冷水坪村碧云洞]’ ( SNUC). Paratype: CHINA: 1 ♀, also from Leng-shui-ping Village and same date, except ‘ Baiyun Cave, 26°20’52.38’’N, 110°19’25.70’’E, 468 m [湖南冷水坪村白云洞]’ ( SNUC).

Diagnosis. Male with simple vertex; antennomeres IX–XI modified; each eye composed of about 45 facets; pronotum with small lateral spines; metaventrite raised above metacoxae to form high projections, with a row of dense setae along each ridge; aedeagus with apical portion of the median lobe split to two parts, dorsal part shorter than ventral part. Female with each eye composed of about 15 facets, and may be identified only when associated with a male.

Description. Male. Body ( Fig. 3A ) reddish brown, mouth parts, antennae and tarsi paler. Body length (combined length of head, pronotum, elytra, and abdomen) 2.80 mm. Length of head from clypeal anterior margin to head base 0.58 mm, width across eyes 0.58 mm; median longitudinal carina extending from base to level of midline of eyes; each eye composed of about 45 facets; antennomeres IX–XI modified ( Fig. 3B ). Pronotum about as long as wide, length along midline 0.62 mm, maximum width 0.61 mm; with small discal and lateral spines. Elytra about as long as wide, length along suture 0.91 mm, maximum width 0.92 mm; discal striae extending to apical 4/5 of elytral length. Metaventrite ( Fig. 3C–D ) strongly raised above metacoxae to form high projections, with rows of dense setae along projections; metacoxa and metatrochanter simple. Abdomen narrower than elytra, length of dorsally visible part along midline 0.69 mm, maximum width 0.79 mm. Aedeagus ( Figs. 3E–F ) asymmetric, length 0.55 mm.

Female. General appearance similar to male. Eyes smaller, each composed of about 15 facets. Antennae and metaventrite simple. Measurements: body length (combined length of head, pronotum, elytra, and abdomen) 2.73 mm, length of head from clypeal anterior margin toward head base 0.55 mm, width across eyes 0.56 mm, length of pronotum along midline 0.61 mm, maximum width of pronotum 0.60 mm, length of elytra along suture 0.83 mm, maximum width of elytra 0.88 mm, length of dorsally visible part of abdomen along midline 0.74 mm, maximum width of abdomen 0.82 mm.

Comparative notes. Thirteen species from China and Thailand have been included in the Tribasodites bedosae species-group (Yin et al. 2015), which exclusively contains cavernicolous species. Using the key provided in Yin et al. (2015), T. biyun could be keyed out at couplet 10 together with T. bama Yin, Nomura & Li. These two species share the spinose pronotal lateral margins, simple metacoxa and metatrochanter, and short rows of setae present only on the posterior half of the metaventrite. Tribasodites biyun is the first species of the T. bedosae group from Hunan Province, and its males can be readily separated from those of T. bama by the simple antennomere VIII, lateral projection of antennomere IX short and not curved, antennomere X less expanded and lacking a large excavation at the base, and the much longer dorsal branch of the apical fork of the aedeagal median lobe. Among the Chinese species, the simple antennomere VIII of T. biyun is shared only with T. abnormalis Yin, Nomura & Li from Guizhou, but males of the latter species possess unmodified antennae, a modified vertex, an unforked apex of the aedeagal median lobe, and thus can be readily separated from T. biyun .

Distribution. China: Hunan.

Etymology. The new specific epithet is taken directly from the name of the cave where the holotype was collected, i.e., Biyun Cave [literally: Bluish Cloud Cave].

Figures

FIGURE 3. Tribasodites biyun, male. A. Dorsal habitus. B. Antennal club. C. Metaventrite. D. Metaventral process, in lateral view. E–F. Aedeagus, in lateral (E), and ventral (F) view. Scale bars: 0.5 mm in A, C; 0.2 mm in B, D–F.