Batraxis liyunchuni, Yin, 2020

Yin, Zi-Wei, 2020, New species of karst-dwelling Pselaphinae from southwestern China (Coleoptera: Staphylinidae), Acta Entomologica Musei Nationalis Pragae 60 (1), pp. 163-168 : 164-165

Batraxis liyunchuni sp. nov.

( Fig. 1 )

Type material. HOLOTYPE:, ‘ CHINA: SW China: Guizhou, Luodian County ( ƤÑH), Ban’geng Town (ṞOiş), Ban’geng Village (ṞOi IJ), Guanyin Cave ( ḴṘḌ), N25°31 ′ 6.84 ′′, E106°38 ′ 54.68 ′′, ca. 540 m, 8.x.2019, Yun-Chun Li leg.’ ( SNUC) . PARATYPE: CHINA: 1 ♀, same label data as holotype ( SNUC).

Diagnosis. Body length approximately 2.0 mm; with long, sparse pubescence; frons broad, with complete subantennal transverse sulcus; vertexal foveae distinct; male antennomere 10 protuberant at anteromesal corner, antennomere 11 with wide impressed area on mesal surface; median gular carina broad and elevated, with two small gular foveae close to each other; metaventrite with paired elongate lateral carinae in male; legs elongate and simple in both sexes; tergite IV with broad basal sulcus which is densely setose at middle, long discal carinae widely separated and sub-paralleled; aedeagus symmetrical, with relatively stout median lobe, parameres distinctly exceeding apex of median lobe.

Description. Male ( Fig. 1A ). Body reddish-brown, length from anterior margin of clypeus to apex of abdomen 2.02 mm. Head rectangular, length from anterior margin of clypeus to head base 0.44 mm, equals to maximum width across eyes; vertex finely punctate, sparsely pubescent, moderately convex, with pair of small vertexal foveae; antennal tubercles raised; frons flattened posteriorly and raised anteriorly at middle, merging with antennal tubercles to form transverse bridge; subantennal transverse sulcus complete; lacking vertexal sulcus connecting foveae; each eye composed of about 25 facets; antennae relatively elongate, length 0.95 mm, with distinct club ( Fig. 1B ) formed by apical two antennomeres; antennomere 1 large, approximately 1.5 times as wide as 2, antennomere 2 cylindrical, antennomeres 3 and 4 successively shorter, narrowed at bases and broadening apically, antennomeres 5–9 short and transverse, antennomere 10 approximately twice as wide as antennomere 9, asymmetrical, with its anteromesal corner distinctly protuberant, antennomere 11 largest, curved mesally, with its mesal surface broadly impressed; median gular carina broad and elevated, with two small nude gular foveae close to each other. Pronotum almost glabrous, with sparse pubescence similar to those of head; length along midline 0.43 mm, maximum width 0.44 mm; with nude median and lateral antebasal foveae. Elytra wider than long, length along suture 0.69 mm, maximum width 0.53 mm, dorsal surface with sparse, long setae; each elytron with two punctiform basal foveae in shallow impressions; sutural stria complete, lacking discal longitudinal sulcus. Legs simple, without protuberances. Abdomen longer than wide, length along midline 0.73 mm, maximum width 0.62 mm; slightly constricted near base; tergite IV (first visible tergite) with broad basal impression, densely setose at middle; discal carinae long, widely separated, almost parallel to each other, about 0.4 times of total tergal length; marginal carinae complete and oblique. Length of aedeagus ( Fig. 1C, 1D ) 0.29 mm (including parameres), median lobe relatively stout, with large, oval diaphragm, parameres distinctly exceeding apex of median lobe, each broadened preapically, narrowed at apex, and with two preapical setae; endophallus comprises two elongate sclerites at middle, and numerous weakly sclerotized spine-like structures anteriorly.

Female. Similar to male in general appearance; antennomere 10 lacking protuberance, antennomere 11 similarly asymmetrical as male, but mesal surface lacking impression; metaventrite lacking lateral carinae; each eye composed of about 12 facets. Measurements (as for male): body length 2.0 mm; length of head 0.44 mm, equals to width; length of pronotum 0.44 mm; maximum width 0.43 mm; length of elytra 0.50 mm, maximum width 0.67 mm; length of abdomen 0.62 mm, maximum width 0.54 mm.

Comparative notes. This is a very distinct species which can be easily separated from all congeners from East Asia by the unique form of the sexually modified antennal club and laterally carinate metaventrite of the male, the simple legs of both sexes (the males of most Batraxis species have modified tibiae or protuberant protrochanters), and the form of the aedeagus.

Etymology. The new species is named after Yun-Chun Li, who collected the type material of the new species.

Distribution. Southwestern China: Guizhou.

Comments. This is the first Batraxis species known to inhabit a cave environment. Both specimens were found walking on the ground in the dark zone of the cave (Y.- C. Li, pers. comm.). However, B. liyunchuni sp. nov. exhibits no particular morphological adaptations (e.g., distinctly elongate appendages, reduction of eyes) as usually found in other obligate troglobitic pselaphines (e.g., Zopherobatrus Yin & Li, 2015 ). With this regard, further field work both in and outside the cave is needed to determinate the biology of this species.

Figures

Fig. 1. Batraxis liyunchuni sp. nov., male. A – habitus; B – antennal club; C, D – aedeagus, ventral. Scale bars: 0.5 mm in A; 0.2 mm in B–D.