Araneibatrus curvitibialis 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 : 590-592

Araneibatrus curvitibialis Yin and Zhou , new species

( Figs 1–2 )

Type material (8 exs). Holotype: CHINA: ♂: ‘ China: Hunan, Shaoyang City, Chengbu Miao autonomous county, Leng-shui-ping Village , Baiyun Cave , 26°20’52.38’’N, 110°19’25.70’’E, 468 m, 10.xi.2017, Gu-Chun Zhou leg. [湖南冷水坪村白云洞]’ ( SNUC) . Paratypes: CHINA: 2 ♂♂, 3 ♀♀, same collecting data as the holotype ; 2 ♀♀: also from Leng-shui-ping Village and same date, except ‘ Biyun Cave , 26°20’33.84’’N, 110°19’45.39’’E, 473 m [湖南冷水坪村碧云洞]’ ( SNUC) .

Diagnosis. Body length 2.28–2.33 mm. Vertex with a short mediobasal carina, lateral postantennal carinae present; clypeus short, less than one-third of total head length. Pronotum with a shallow median longitudinal impression and transverse antebasal sulci, with dorsal carinae and antebasal protuberances. Elytra with shallow, indistinct discal striae. Tergite IV with two mediobasal and four basolateral foveae. Sternite IV (second visible sternite) with two mediobasal and six basolateral foveae. Male with antennomeres IX–X, protarsomere II, apices of the mesofemur, mesotibia, and metatibia modified. Aedeagus with a large and transverse basal capsule.

Description. Male ( Fig. 1A ). Body length (combined length of head, pronotum, elytra, and abdomen) 2.28– 2.33 mm. Body uniformly reddish-brown, mouthparts, tibiae, and tarsi paler. Head ( Fig. 2A ) about as long as wide, length from clypeal anterior margin to head base 0.46 mm, width across eyes 0.43–0.44 mm, finely punctate; vertex with short median carina extending from near posterior margin of head toward level slightly past mid-length of eyes; pair of lateral postantennal carinae extending from posterior margins of antennal tubercles toward postocular margins; clypeus relatively short, slightly more than one-fifth of total head length. Each eye composed of about 35 facets. Antennal club formed by three apical enlarged antennomeres ( Fig. 2B ), antennomeres IX and X enlarged and concave at mesal surfaces, XI asymmetrically narrowed at apical one-third. Pronotum ( Fig. 2A ) slightly narrower than head, longer than wide, length along midline 0.49 mm, maximum width 0.41–0.42 mm; disc coarsely punctate, with wide and shallow median longitudinal impression and transverse antebasal sulcus, with dorsal carinae and antebasal tubercles. Elytra slightly longer than wide, length along suture 0.73–0.75 mm, maximum width 0.70–0.71 mm, with shallow discal striae at basal third. Metaventrite lacking modification. Protarsomere II expanded at ventral margin near middle ( Fig. 2C ); apex of mesofemur roundly projected at ventral margin ( Fig. 2D ); apex of mesotibia with large, acute spine ( Fig. 2E ); metatrochanter distinctly projected ventrally ( Fig. 2E ); metatibia strongly curved, with long pubescence at middle and dilated at apical third ( Fig. 2G ). Length of dorsally visible part of abdomen along midline 0.58–0.65 mm, maximum width of abdomen 0.62 mm. Tergite IV with complete and oblique inner marginal carinae; basal impression subdivided into three parts by one pair of mediobasal and two pairs of basolateral foveae, tergites V–VII each with one pair of basolateral foveae. Sternite IV (second visible sternite) with one pair of mediobasal and three pairs of basolateral foveae, sternites V–VII each with one pair of basolateral foveae. Length of aedeagus ( Fig. 2H–J ) 0.31 mm, median lobe with stout and slightly transverse basal bulb and large foramen; apex of elongate median lobe deeply narrowed; dorsal lobe broad, apex truncate.

Female. General appearance similar to male. Antennae and legs lacking modifications. Eyes smaller, each composed of about 8 facets. Elytra relatively shorter. Measurements: body length (combined length of head, pronotum, elytra, and abdomen) 2.73–2.80 mm, length of head from clypeal anterior margin toward head base 0.48 mm, width across eyes 0.45 mm, length of pronotum along midline 0.49 mm, maximum width of pronotum 0.42 mm, length of elytra along suture 0.70 mm, maximum width of elytra 0.68–0.69 mm, length of dorsally visible part of abdomen along midline 0.63–0.66 mm, maximum width of abdomen 0.64–0.65 mm.

Comparative notes. Using the key in Yin et al. (2016), the new species could be keyed out at couplet 4 together with A. grossepunctatus Yin, Jiang & Li. These two species share a similar external morphology of the head and pronotum, a similar form of the aedeagal basal capsule, and a close distribution (both in southern Hunan). However, the unique structures of antennomeres IX–X, protarsomere II, apex of the mesofemur, metatrochanter, and metatibia in the male of A. curvitibialis , and the configuration of the aedeagal median and dorsal lobes readily separate the new species from A. grossepunctatus , as well as from all other congeners of the genus.

Distribution. China: Hunan.

Etymology. The new specific epithet refers to the curved metatibiae of the male of the new species, which are a species characteristic.

Figures

FIGURE 1. Dorsal habitus of Araneibatrus curvitibialis. A. Male. B. Female. Scale bars: 0.5 mm.

FIGURE 2. Male diagnostic features of Araneibatrus curvitibialis. A. Head dorsum and pronotum. B. Antennal club. C. Protarsus. D. Mesotrochanter and mesofemur. E. Apical portion of mesotibia. F. Metatrochanter. G. Metatibia. H–J. Aedeagus, in dorsal (H), lateral (I), and ventral (J) view. Scale bars: 0.3 mm in B, D, G; 0.2 mm in A; 0.1 mm in C, E–F, H–J.