Xuedytes bellus Tian & Huang

Tian, Mingyi, Huang, Sunbin & Wang, Dianmei, 2017, Discovery of a most remarkable cave-specialized trechine beetle from southern China (Coleoptera, Carabidae, Trechinae), ZooKeys 725, pp. 37-47 : 39-41

Xuedytes bellus Tian & Huang sp. n. Figs 1, 2, 3, 4, 5

Holotype.

Male, Cave II, southeastern Du’an Yao Autonomous County, Hechi Shi (=Prefecture), northern Guangxi Zhuang Autonomous Region, southern China, VIII-08-2017, leg. Mingyi Tian, Sunbin Huang, Dianmei Wang and Mengzhen Chen; paratypes: 2 males and 1 female, IBID. All type material is deposited in the insect collection of South China Agricultural University, Guangzhou.

Diagnosis.

A large-sized, blind, cave-adapted trechine, remarkably modified morphologically, with both prothorax and elytra highly elongated and slender so that body five times longer than wide, antennae slightly shorter than body including mandibles, extending beyond elytral apices; head, pronotum and base of elytra covered with sparse erect setae. Habitus as in Figs 1 and 3.

Description.

Length: 8.3-9.0 mm (from apex of right mandible to elytral apex) or 7.5-8.6 mm (from labrum to elytral apex); width: 1.4-1.5 mm.

Body yellowish brown, but antennae, palps and tarsi pale; strongly shining; head, pronotum and base of elytra covered with rather long and sparse setae, other parts of elytra glabrous, underside of fore body excluding pleurae, meso- and metasterna pubescent, abdominal ventrites densely pubescent; microsculptural engraved meshes transverse striate on head, pronotum and elytra; fore body very strongly elongated, much longer than elytra, (HLm+PrL)/EL = 1.55-1.60.

Head oblong subquadrate, much longer than wide, HLm/HW = 3.02-3.03, HLl/HW = 2.02-2.04; genae fairly well developed, broadly dilated on sides, widest at about middle of head from neck to clypeal margin, gradually tapered posteriorly; frons and vertex moderately convex, frontal furrows moderately defined, strongly diverging posteriorly, ending level with middle frontal pores; clypeus transverse, 6-setose; labrum transverse, frontal margin nearly truncate, 6-setose; three pairs of frontal setiferous pores present; mentum and submentum completely fused, mentum bisetose on either side of tooth at base, mental tooth short and blunt at apex, basal fovea broadly concave; submentum 8-setose; palps thin and very slender, glabrous except for labial palpomere 2 which is bisetose on inner margin; 2nd labial palpomere 1.40 times longer than 3rd; 3rd maxillary palpomere 1.25 times longer than 4th; suborbital pore much closer to base than to submentum (Fig. 2). Antennae thin and very long, 1st antennomere shortest and stoutest, 4th longest, 11th longer than 10th, length ratios of antennomere 1 to 11 as 1.00 / 1.36 / 3.07 / 3.55 / 2.77 / 2.81 / 2.52 / 2.10 / 1.94 / 1.65 / 1.94.

Prothorax (Fig. 3a) much longer than head including mandibles, PrL/HLm = 1.15-1.17, PrL/HLl = 1.70-1.72, widest at about 1/5 off base, nearly 3 times as long as wide, PrL /PrW = 2.94-2.95, slightly wider than head, PrW/HW = 1.18-1.19, evidently wider than pronotum, PrW/PnW = 1.27-1.30. Pronotum very strongly elongated, tube-like in front half which is narrow and nearly parallel-sided; convex at about basal 1/5 where the widest point lies, then gently sinuate before hind angles which are obtuse and rectangular, fore angles rounded; nearly four times longer than wide, PnL/PnW = 3.84, slightly narrower than head, PnW/HW = 0.91-0.92, base slightly concave, wider than front, PbW/PfW = 1.27, front convex; lateral sides finely bordered throughout, base and front unbordered; basal latero-marginal setae absent, two latero-marginal setae present in about middle portion, with three or four additional short setae in fore part; disc strongly convex in front and moderately convex in basal half, deeply concave a little before middle; median line clear, but shallow, basal transverse impression well-marked, short; scutellum fairly large.

Elytra (Fig. 3a) very strongly elongated ovate, much longer than wide, EL/EW = 2.46; longer than prothorax, EL/PrL = 1.58-1.59, almost twice as wide as prothorax, EW/PrW = 1.90-1.91; distinctly dilated posteriorly, widest at about 3/5 of elytra off base, lateral sides smooth, not ciliate, finely bordered throughout, marginal gutters well-marked; disc distinctly convex, but evidently concave near base; striae virtually missing, yet more or less traceable, intervals moderately convex. Chaetotaxy (Fig. 3a): dorsal pores with stout and long setae, two dorsal setiferous pores present on 3rd stria at about 1/3 and 3/5 of elytra off base, respectively; pre-apical pore at about apical 1/6 of elytra, much closer to elytral suture than to apical margin; basal pore located between scutellum and marginal gutter; marginal umbilicate pores not aggregated, pores 1-3 and 10 near marginal gutter, other pores distant from gutter; humeral groups with pores 1 and 4 widely isolated, 2 and 3 close to each other, distance from pore 4 to 3 subequal to 5; middle group closely spaced, distance of pore 5 and 4 subequal to that of pore 5 and 6; apical group composed of four pores.

Legs slender and long, bearing short pubescence; fore and middle femora sparsely setose; fore tibia smooth, with neither a longitudinal furrow nor a sulcus; 1st tarsomere shorter than, slightly longer than, and much longer than 2 nd– 4th tarsomeres combined in fore, middle, and hind legs, respectively.

Male genitalia (Fig. 4a, b). Aedeagus quite small and short, distinctly curved ventrally in middle portion in lateral view, then broad at apex; inner sac with a fairly large copulatory piece, the latter about 1/3 as long as median lobe; base quite large, open ventrally, with a hyaline sagittal aileron; in dorsal view, apical lobe fairly stout, slightly sinuate on right side, rounded at apex. Parameres short and quite elongated, each bearing four long apical setae.

Etymology.

“Bellus”, in Latin meaning “beautiful”, to refer to this beautiful aphaenopsian beetle.

Distribution.

China (Guangxi: Du’an). Known only from Cave II.

This cave maintains a natural condition, opening on a small hill on the northern bank of the Hongshui River. The entrance is surrounded by dense bushes and not readily accessible (Fig. 5a, b). The total length of the cave is still unknown, but said to be about 200 m, according to local people. It is sufficiently wet inside the gallery and is good for cave fauna. The beetles were found running on walls and stalactites (Fig. 5c, d), sympatric with spiders (Fig. 5e, f), millipedes (Fig. 5g, h), woodlice (Fig. 5i) and crickets (Fig. 5j).