Saturday, January 6, 2018

[Entomology • 2017] Xuedytes bellus • A Most Remarkable Cave-specialized Trechine Beetle (Coleoptera, Carabidae, Trechinae) from southern China

Xuedytes bellus  Tian & Huang, 2017

in Tian, Huang & Wang, 2017

Xuedytes bellus Tian & Huang, gen. et sp. n. is described from a limestone cave in Du’an Karst of Guangxi, a kingdom of cavernicolous trechine beetles in southern China. From a morphological point of view, Xuedytes Tian & Huang, gen. n. seems to be the most extremely cave-adapted trechines in the world. Superficially, it looks much like Giraffaphaenops Deuve, 2002 in general body shape, in particular the structure of the prothorax, but simultaneously it is similar to Dongodytes (s. str.) Deuve, 1993, based on elytral characters, including chaetotaxy. Hence the new genus seems to represent a lineage intermediate between Giraffaphaenops and Dongodytes (s. str.).

Keywords: aphaenopsian, Guangxi, ground beetle, troglobite

Figure 1. Habitus of Xuedytes bellus Tian & Huang, gen. et sp. n., holotype male.
Figure 2. Head (ventral) of Xuedytes bellus, a paratype female.

Taxonomic treatment

Xuedytes Tian & Huang, gen. n.
 Type species: Xuedytes bellus Tian & Huang, sp. n.

Generic characteristics: Highly modified aphaenopsian trechines, body shape, in particular prothorax, similar to that in Giraffaphaenops, but elytra generally like in Dongodytes (s. str.) (Fig. 1); large-sized, with body (especially prothorax and elytra) and appendages thin and extremely elongated, eyeless and unpigmented; fore body part (head including mandibles, plus prothorax) much longer than, or as long as (excluding mandibles) elytra, respectively; body smooth; three pairs of frontal setiferous pores present on head; mandibles thin and elongated, feebly curved apically, longer than head width, right mandible edentate; labial suture completely missing; mentum bisetose on either side of tooth at base, base broadly concave; mental tooth simple, short and blunt at tip; submentum 8-setose; ligula bisetose at apex (Fig. 2); antennae very long, antennomeres 10 and 11 extending beyond elytral apices. Prothorax similar to that of Giraffaphaenops, wider than head, very strongly elongated, much longer than head including mandibles, propleura distinctly tumid in basal 1/3, visible from above; pronotum barrel-shaped, thin and distinctly elongated, lateral margins visible throughout from above, slightly narrower than head; hind latero-marginal setae absent, but two long latero-marginal setae plus two or three additional short setae present from middle to front. Elytra similar to those in Dongodytes (s. str.), narrow anteriorly and dilated posteriorly, side margins narrowly bordered throughout, shoulders lacking; striae virtually missing, only weakly traceable; two dorsal and the pre-apical setiferous pores present, each with a very long seta; chaetotaxy similar to that in Dongodytes (s. str.). Protibia smooth, without longitudinal sulcus; protarsomeres not modified in male. Ventrites VII bisetose apically in male, but quadrisetose in female. Male genitalia moderately sclerotized, small, strongly curved ventrally in lateral view, with a quite large and thin sagittal aileron; apical lobe wide and broad in dorsal view; parameres much shorter than median lobe, yet well-developed.

Etymology: “Xue + dytes”. “Xue” in Chinese means “cave”, to indicate that the beetles are cavernicolous. Gender masculine.

Generic range: China (Guangxi Zhuang Autonomous Region).

Xuedytes bellus Tian & Huang, sp. n.

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.

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

Figure 5.  Cave II, southeastern Du’an, the type locality of Xuedytes bellus, and sympatric cave animals
 a, b cave environs and opening c a chamber in the cave where the beetles were collected d a running beetle in cave e, f cave spiders g, h cave millipedes i a cave woodlouse j a cave cricket. 

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).

 Mingyi Tian, Sunbin Huang and Dianmei Wang. 2017. Discovery of A Most Remarkable Cave-specialized Trechine Beetle from southern China (Coleoptera, Carabidae, Trechinae).  ZooKeys. 725: 37-47.  DOI: 10.3897/zookeys.725.21040