Ckacus youcha, Tian & Huang, 2021

Tian, Mingyi & Huang, Sunbin, 2021, Discovery of a new cavernicolous trechine genus and species from a deep pit in Anlong, southwestern Guizhou Province (Coleoptera: Carabidae: Trechinae), Zootaxa 4985 (2), pp. 194-202 : 196-201

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Ckacus youcha

n. sp.

Ckacus youcha n. sp.

(Chinese name: 油ë喀Ḇù步ffl)

( Figs. 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Type material. Holotype male, Luoshui Dong cave, Xianheping, Anlong Xian (County), Qianxinan Miao & Buyi Zizhizhou (Autonomous Prefecture), southwest Guizhou, 105°35’31.42’’E, 24°59’16.11’’N, 1163 m, 2020-XII-06, leg. Huanghe Zhou (“You Cha”), in SCAU. GoogleMaps

Diagnosis. A medium-sized semi-aphaenopsian trechine species, wholly pubescent, with moderately elongated body and thin appendages.

Description. Length: 7.0 mm, width: 2.0 mm. Habitus as in Fig. 2 View FIGURE 2 .

Body yellowish-brown, but palps and tarsi yellow; wholly covered with long setae, moderately shining, underside of head with a few setae, thorax glabrous ventrally but prosternum with several setae, abdominal ventrites shortly and densely pubescent. Macrosculpture: transversely meshed on head, densely and transversely striate on pronotum and elytra.

Head much longer than wide, HLm/HW = 2.1, HLl/HW = 1.6; widest at about middle of head excluding mandibles, neck constriction well-marked; frons and vertex moderately convex; frontal furrows shallow and short, ended at about middle of head; anterior and posterior supraorbital pores located at middle and basal 1/4 of head respectively; clypeus 6-setose; labrum transverse, frontal margin straight, 6-setose; mentum bisetose on either side of tooth base, tooth moderately long, unified at tip; ligula thick and short, 8-setose at apex, inner two much longer than other; palps thin and elongate, all glabrous but bisetose on inner margin of 2 nd labial palpomere and two additional setae at outer margin medially and subapically, penultimate palpomere longer than the apical one in labium and maxillaries (cf. 1.2 times); suborbital pores intermedially sited; antennae slender, 1 st antennomere with several cilia then densely pubescent from the 2 nd antennomere, 1 st stouter than others, as long as 2 nd, 3 rd the longest, relative length of each antennomere as follows: the 1 st (1.0), 2 nd (1.0), 3 rd (1.9), 4 th (1.8), 5 th (1.7), 6 th (1.7), 7 th (1.5), 8 th (1.5), 9 th (1.3, 10 th (1.1) and 11 th (1.5).

Propleura invisible from above. Pronotum slightly longer than wide, PnL /PnW = 1.1, shorter than head excluding mandibles, PL/HLl = 0.8; lateral margins finely bordered throughout; widest at about 1/3 from front, gently contracted forwards and backwards, contracted and nearly straight near hind angles which are acute; fore angles slightly protruded, nearly acutangular; base faintly bisinuate, front nearly straight, both unbordered, front slightly wider than base, PfW/PbW = 1.2; anterior and posterior latero-marginal setae at 5/6 from base and just before hind angles respectively; disc moderately convex, mid-line distinct. Scutellum small and narrow.

Elytra slightly longer than fore body including mandibles, much longer than wide, EL/EW = 1.7, twice as wide as pronotum; base unbordered, lateral margins finely ciliate throughout, nearly obliquely truncate at humeral portions, humeral angles broad, widest a little behind middle of elytra; disc strongly convex; basal pore present at sides of scutellum, anterior and posterior dorsal pores on the 3 rd stria at basal 1/4 and middle of elytra respectively, preapical pore at exactly the anastomotic point between the 2 nd and 3 rd striae, closer to elytral suture than to apical margin; locations of umbilicate marginal pores as in Fig. 3A View FIGURE 3 .

Legs densely pubescent; 1 st and 2 nd protarsomeres slightly widened in male, shortly and bluntly denticulate at inner apex; 1 st tarsomere much shorter than 2 nd –4 th combined in fore legs, whereas as long as in middle and hind legs; tibiae without longitudinal sulci.

Each abdominal ventrites V-VI bisetose paramedially, VII bisetose in male.

Male genitalia ( Fig. 3B, C View FIGURE 3 ): The median lobe of aedeagus medium-sized, quite elongate, gently arcuate towards apex which is sharp; basal opening quite small, with a large and almost rounded sagittal aileron; inner sac armed with a long copulatory piece, which is about 1/4 as long as aedeagus; in dorsal view, apical lobe thin, much longer than wide, broadly rounded at apex; parameres well-developed, but much shorter than median lobe, each paramere with four long setae at apex.

Etymology. Dedicated to “You Cha”, a nickname of Ms. Huanghe Zhou, an active member of Guilin Cave Exploration Team, Guilin.

Distribution. China (Guizhou). Known only from the limestone cave Luoshui Dong, sympatric with Satotrechus rieae Uéno, 2006 .

Luoshui Dong is located within Xianheping Forest Park. This vertical pothole is 515 m deep, one of the deepest caves in China ( Figs. 4 View FIGURE 4 , 5A, B View FIGURE 5 ). There is a lot of debris in the muddy terrace of about 400 m below the entrance. The specimens sampled, as well as many other Trechini, observed wandering on the ground and walls between - 330 m to - 450 m ( Fig. 4 View FIGURE 4 ). Apart from beetle species, other animals living inside the cave were cricket Tachycines (Gymnaeta) sp., millipedes of the genera Glyphiulus and Paracortina , harvestmen, bats, frog Oreolalax rhodostigmatus Hu & Fei, 1979 and crab Diyutamon cereum Huang et al., 2017 ( Fig. 5 View FIGURE 5 C-E).