Sinometrius donggongensis Song & Peng, new species 洞宫Ŗ灼步Ƥ

Type material. Holotype ♂, CHINA, labeled ‘China, Zhejiang, Lishui City, Qingyuan County (Ṅ元B), Baishanzu N. R. (百Ɯ祖), 27°45′25″N, 119°12′06″E, elev. 1700 m, 1‒2-v-2014, Xiao-Bin Song & Zhong Peng leg. / HOLOTYPE [red], Sinometrius donggongensis sp. nov., det. Song & Peng, 2020’ (SNUC). Paratypes: CHINA: 1♂, 1♀, same data as holotype; 1♂, labeled ‘ China, Zhejiang Prov., Lishui, Longquan City, Fengyangshan (凤DƜ), Longquanshan (AEṜƜ 风AEḴ), Fengyang Lake (凤Ddz), 27°87′40″N, 119°18′55″E, elev. 1550 m, 26-iv-2014, Zi-Wei Yin leg.’ All paratypes are housed in SNUC, and bear the following label: ‘Paratype [yellow], Sinometrius donggongensis sp. nov., det. Song & Peng, 2020’.

Diagnosis. The new species can be readily separated from Sinometrius turnai, by the following characters: 1) first galeomere almost as long as the 2nd, 3rd antennal segment longer than the 4th; 2) terebral tooth of both left and right mandible well-developed; 3) median tooth of mentum rounded at apex and its length approximately half the length of the internal margin of the lateral lobes; 4) lateral margins of the pronotum more sinuate posteriorly; 5) different shape of the aedeagus. It can be readily distinguished from S. jaroslavi by 1) the slender pronotum; 2) lateral margins of the pronotum more sinuate posteriorly; 3) striae distinct, formed by shallowly engraved punctures.

Description. Body reddish-brown to piceous, mouthparts and legs lighter.

Male head (Fig. 1) approximately quadrate, slightly convex. Clypeus sparsely punctate, with isodiametric reticulate microsculpture, anteriorly slightly convex at middle, anterolaterally with two long setae, clypeal suture distinct. Frons sparsely and irregularly punctate, with transverse wrinkles beside keel-like elevation. Vertex moderately punctate, with isodiametric reticulate microsculpture, at front with irregular shallow depression. Eyes somewhat small.

Antennomeres clavate, antennomere 1 thick, about 1.5 times as wide as the second, antennomeres 1–4 sparsely covered with yellow setae except at the base, antennomeres 5–11 moderately covered wioth yellow setae, 11th antennomere densely covered with very short sensory setae. Labrum rectangular, anterior margin slightly bisinuate, with 8–12 long setae anteriorly. Left mandible (Fig. 2A) with a scrobal seta apically, with long incisor tooth, terebral tooth long, blunt at tip, anterior retinacular tooth triangular and blunt. Right mandible (Fig. 2B) with a scrobal seta apically, terebral tooth distinct, triangular and blunt. Cardo of maxilla (Fig. 2C laterally with one seta. Basistipes laterally with one long posterior seta. Palpifer with one seta laterally. Lacinia with apical tooth thick and fairly acute, curved mediad. Galeomere I almost as long as galeomere II. Maxillary palpomere II and III with some setae near apex. Labium (Fig. 2D) with mentum tooth well developed, bifid, rounded apically; lateral lobes laterally sinuate. Ligula (Fig. 2D) with apical margin of glossal sclerite subtruncate, with two pair of setae apically. Palpiger long. Labial palpomere II with two long setae at internal margin.

Pronotum (Fig. 1) moderately punctate, with isodiametric reticulate microsculpture; anterior margin excavated, anterior angles prominent, lateral margins moderately sinuate posteriorly, posterior margin emarginated near hind angles; median longitudinal impression distinct, shallow, becoming indistinct toward anterior and posterior borders.

Elytra (Fig. 1) convex, glossy, with isodiametric reticulate microsculpture, sparsely covered with fine punctures; striae consisting of rows of engraved punctures more deeply impressed than the surrounding punctures; lateral fold absent. Hind wings fully reduced. Protarsomeres 1–3 somewhat dilated, 2nd and 3rd segments transverse, scutiform. Sternite VII (Fig. 3E) wide, widely truncate, slightly excavate; ring sclerite (Fig. 3D) ovate, hemicircular apically, and laterally on each side bears the explosion chambers, hemisternite large..

Median lobe of aedeagus short, rather strongly arcuate in lateral view, basal bulb open widely, apical part almost rectangularly bent ventrad in lateral view, base of internal sac with a long sclerotization(Fig. 3A); right paramere (Fig. 3B) arcuate, apical lobe with some long hairs along ventral margin; left paramere large, (Fig. 3C) strongly tapered distally, subapically and apically with several short spines.

Female protarsomeres 1–3 narrowed, 2nd and 3rd segments trapezoid. Sternite VII (Fig. 3F) excavated in the middle, with posterior margin narrower and more acute. Gonopods IX monomeric, furcate behind the subapical setose organ.

Measurements. BL, 8.67–9.56; HW, 1.78–2.08; EL, 0.36–0.39; PW, 2.59–2.95; PBaW, 2.31–2.61; PL, 1.74–1.93; ELW, 4.09–4.39; ELL, 5.56–5.84; PW/PL, 1.39–1.56; PW/PBaW, 1.08–1.13; PW/HW, 1.38–1.51; ELL/ELW, 1.29–1.40.

Distribution. South Zhejiang, China.

Biology. Like its congener, the new species only lives in the montane zone at elevations of 1500–1700 m. Individuals from Baishanzu were collected from original forest, filled with leaf litter of Fagaceae and Yushania baishanzuensis (bamboo) (Fig. 4A). One male adult was sifted from coniferous forest near Fangyang Lake (Fengyangshan).

Di Giulio and Muzzi reported Sinometrius turnai as a partial myrmecophage based on their personal observations and the remains of an ant in the beetle’s gut (Muzzi et al., 2019). We transported three living adults (Fig. 4B) to the laboratory for behavioral experiments, and fed them several dead mealworm larvae (Tenebrio molitor (Linnaeus, 1758)), bodies of Japanese carpenter ants (Camponotus japonicus Mayr, 1886) or injured American cockroach nymphs (Periplaneta americana (Linnaeus, 1758)) per three days. All of these foods were well-accepted by the beetles. In addition, before we ended the rearing, one female adult was devoured by other two individuals (probably after death). The above observations suggest that Sinometrius donggongensis is probably a free-living predatory ground beetle that also feeds on ants.

Etymology. The new specific name refers to the type locality, i. e., the Donggong mountains (洞宫Ɯ脉).