Batriscenaulax campestris, Yin, 2022

Yin, Zi-Wei, 2022, The Batrisini of Tibet: unveiling an enigmatic ant-loving beetle diversity at Earth’s “ Third Pole ” (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5111 (1), pp. 1-211 : 69-71

Batriscenaulax campestris sp. nov.

( Fig. 29 , 80A , 99A )

Chinese common name: 低地ậḇà甲

Type material (2 exx.). HOLOTYPE: CHINA: ♂ , ‘ China: Tibet, Mêdog County, Beibeng Vill. (Ü崩村, ca. 29°14’36”N, 95°10’22”E), 800-1000 m, 01.viii.2014, Wen-Xuan Bi leg.’ ( SNUC) . PARATYPE: CHINA: 1 ♂, same data as that of holotype ( SNUC) .

Diagnosis. Male. Body length approximately 1.80–1.85 mm. Head sub-rectangular at base; vertexal foveae large and asetose, lacking sulcus connecting them; antenna elongate; antennomeres slightly elongate, lacking modifications. Discal stria of elytron long, extending posteriorly to approximately apical 15.5% of elytral length. Protibia with triangular setose brush at apicomesal margin; mesotibia with relatively long apical spine. Tergite 1 (IV) modified, with semi-cinquefoil central cavity and trichomes inside or along margins, with small setose patches lateral to cavity. Aedeagus strongly asymmetric; median lobe with constricted basal capsule and small foramen, ventral stalk broad and bi-sinuate, pointed towards apex; dorsal lobe elongate, flat in lateral view, narrowing towards apex.

Description. Male. Body ( Fig. 29A ) length 1.81–1.86 mm; color reddish-brown, antennae, tibiae, tarsi and mouthparts lighter. Dorsal surface of body covered with short pubescence.

Head ( Fig. 29B ) rounded triangular, sub-rectangular at base, slightly wider than long, length 0.35–0.36 mm, width across eyes 0.42–0.43 mm; vertex finely punctate, with large, asetose vertexal foveae (dorsal tentorial pits), lacking U-shaped sulcus connecting foveae, mediobasal carina short, faint; antennal tubercles moderately raised; frons slightly impressed medially, confluent with clypeus; clypeus smooth, its anterior margin carinate and moderately raised; ocular-mandibular carina complete, weakly presented. Venter with small gular foveae (posterior tentorial pits) narrowly separated, with distinct median carina extending from foveae anteriorly to mouthparts. Eyes strongly prominent, composed of approximately 30 large ommatidia. Antenna moderately elongate, length 0.96–1.09 mm, simple, club formed by moderately enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–8 each elongate, 8 shortest, 9 much larger than 8, 10 as long and as wide as 9, 11 largest, slightly shorter than 9 and 10 combined, sub-conical.

Pronotum ( Fig. 29B ) approximately as long as broad, length 0.45–0.46 mm, width 0.47–0.48 mm, widest at middle; lateral margins rounded; disc slightly convex, finely punctate, median longitudinal sulcus broad, approximately as long as semicircular lateral sulci in dorsal view, the latter extending from dorsal surface laterally and posteriorly and then fusing with lateral ends of antebasal sulcus; lacking median antebasal fovea or mediobasal carina, lateral antebasal foveae connected by transverse antebasal sulcus; outer and inner pair of basolateral foveae distinct. Prosternum with anterior part as long as coxal part, with small lateral procoxal foveae; hypomeral ridge short, present only at basal part, with lateral antebasal hypomeral impression; margin of coxal cavity weakly carinate.

Elytra much wider than long, length 0.65–0.67 mm, width 0.77–0.80 mm; each elytron with two large, asetose basal foveae, lacking subbasal fovea; discal stria long, carinate, extending from outer basal fovea to approximately apical 15.5% of elytral length; humerus angulate, with small subhumeral fovea at middle of elytral flank, sulcate marginal stria extending from fovea to posterior margin of elytron, with thin, curved carinate sulcus extending anteriorly from fovea to humerus.

Mesoventrite short, demarcated from metaventrite by ridged anterior edges of impressed areas where lateral mesocoxal foveae situated at mesal margins, with pair of thin admesal carinae; setose median mesoventral foveae widely separated, lateral mesoventral foveae large and setose, broadly forked internally; intercoxal process short. Metaventrite broadly impressed at middle, admesal areas moderately prominent; with large, setose lateral mesocoxal foveae and pair of smaller, setose lateral metaventral foveae, posterior margin broadly emarginate, lacking split at middle.

Legs moderately elongate; protrochanter with tiny ventral protuberance, protibia ( Fig. 29C ) with small triangular setose brush at apicomesal margin; mesotibia ( Fig. 29D ) with relatively long spine at apex.

Abdomen compressed, widest at lateral margins of tergite 1 (IV) ( Fig. 29E ), length 0.47–0.50 mm, width 0.71–0.72 mm. Tergite 1 (IV) in dorsal view longer than tergites 2–4 (V–VII) combined, setose basal sulcus separated by mediobasal and two pairs of basolateral foveae, lacking discal carinae, semi-cinquefoil central cavity deep, with pair of trichomes along anterior margin, inside cavity one transverse projection and two long trichomes, with small setose patch lateral to each side of cavity, with thin, complete marginal stria; tergites 2 and 3 (V and VI) lacking foveae, 4 (VII) twice as long as 2 and 3 combined along middle, with one pair of basolateral foveae, tergite 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) with mediobasal and two basolateral foveae, with pair of long, thick lateral carinae; midlength of sternite 2 (IV) as long as sternites 3–5 (V–VII) combined, 3 and 4 short, 5 slightly longer than 4, 3–5 lacking foveae, sternite 6 (VIII) transverse, posterior margin emarginate at middle, sternite 7 (IX) ( Fig. 29F ) weakly sclerotized, apex rounded and with few long setae along apical margin.

Aedeagus ( Fig. 29G, H ) 0.27 mm long, strongly asymmetric; median lobe with constricted basal capsule and small, round foramen, ventral stalk broad at base, bi-sinuate, narrowing towards apex; dorsal lobe strongly bent at middle, flat in lateral view, with narrowed apex; parameres reduced to single broad membranous structure.

Female. Unknown.

Comparative notes. This species resembles its five Japanese congeners that have the male protibiae with an apical setose brush and a modified tergite 1 (IV). Batriscenaulax campestris can be readily separated by the larger elytra in relation to the head and pronotum, the apical brushes located on the mesal margin of the protibiae, and the more strongly sinuate ventral stalk of the aedeagus. All the Japanese species of Batriscenaulax have the male protibiae moderately to strongly swollen near their apices, and have the preapical setose brush located on the lateral margins of the tibiae.

Distribution. Mêdog County, Tibet, SW China ( Figs 80A , 99A ).

Etymology. The specific epithet is a Latin adjective meaning ‘field, plain’, indicating the species was collected from a lowland area of Tibet.

Figures

FIGURE 29. Morphology of Batriscenaulax campestris sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Apical part of protibia. D. Apical part of mesotibia. E. Tergite 1 (IV). F. Sternite 7 (IX). G, H. Aedeagus, ventral (G) and lateral (H). Scale bars: 0.5 mm in A; 0.3 mm in B; 0.1 mm in C, D, G, H; 0.2 mm in E, 0.05 mm in F.

FIGURE 80. Distribution of Tibetan Batrisini. A. Batriscenaulax campestris sp. nov. B. Batrisiella acclivis sp. nov. (circle), B. beibeng sp. nov. (triangle), B. bomea sp. nov. (square) and B. concisa sp. nov. (cross). C. B. curvitibialis sp. nov. (circle), B. ganma sp. nov. (triangle), B. guttata sp. nov. (square) and B. zhujianqingi (diamond).

FIGURE 99. Environment of and collecting sites at Nyingchi area. A. Beibeng Township (Ü崩乡). B. Road near Gelin Village (格ff村). C. A bridge at Yarang (亚ü). D. A village near Guoguotang Great Bend (果果Ƌkm弯). E. Environment near Mêdog County (ẸṘ县). F. Path to Renqingbeng Temple (仁ů崩寺). G. An overall view of Guoguotang Great Bend. Photo Credit: E, F by Xiao-Bin Song.