Three new species of the Stenus cirrus group (Coleoptera, Staphylinidae) from Jiangxi, South China

Abstract Three new species from Jiangxi, China, are described and illustrated: Stenus wugongshanus sp. n., Stenus mingyueshanus sp. n., and Stenus songxiaobini sp. n. A previously published key to the Chinese species of the Stenus cirrus group is modified to accommodate the new species.


Introduction
The speciose Stenus cirrus group currently holds 63 species worldwide, 46 of them are known to occur in China and two in Jiangxi. Members of the group are characterized by the presence of long and erect setae on the abdomen. A detailed definition of the group was given in Tang et al. (2008) and Puthz (2009).
Among the specimens we recently collected in the Luoxiao Mountains, Jiangxi Province, three species are recognized as new and are described herein.

Material and methods
For examination of the male genitalia, the apical three abdominal segments were detached from the body after softening in hot water. The aedeagi, together with other dissected parts, were mounted in Euparal (Chroma Gesellschaft Schmidt, Koengen, Germany) on plastic slides. Photos of sexual characters were taken with a Canon G9 camera attached to an Olympus CX31 microscope; habitus photos were taken with a Canon macro photo lens MP-E 65 mm attached to a Canon EOS7D camera.
The type specimens treated in this study are deposited in the following collections: Brachypterous. Head blackish, body reddish brown, each elytron with a large illdefined orange spot, which is about 2/3 as long and about 1/2 as broad as the respective elytron, abdomen shiny; antennae reddish yellow, club infuscate; maxillary palpi and legs reddish yellow; clypeus brown, labrum reddish brown; moderately sparsely pubescent. Paraglossae oval.
Head 1.17-1.22 times as wide as elytra; interocular area with two deep longitudinal furrows, median portion slightly convex, not reaching level of inner eye margins, with a broad impunctate line along midline; punctures round, slightly larger in median portion than near inner margins of eyes, diameter of large punctures about as wide as apex of 2nd antennal segment in cross section, interstices between punctures faintly microsculptured, narrower than half the diameter of punctures. Antennae, when reflexed, slightly extending beyond posterior margin of pronotum, antennomeres III-VIII distinctly narrower than II; IX-XI gradually broadened, forming loose club; relative length of segments from base to apex as 10.5: 6.5: 13.0: 7.5: 7.0: 5.0: 5.5: 3.5: 5.0: 6.0: 6.5.
Pronotum 0.95-1.00 times as long as wide, widest near middle and constricted at base; disk uneven, with distinct median longitudinal furrow of about half the length of pronotum and with an impunctate line along the middle; punctures round and moderately confluent, variable in size, diameter of large punctures about as wide as middle of 2nd antennal segment in cross section, interstices with dense microsculpture, much narrower than half the diameter of punctures.
Elytra 0.92-0.97 times as long as wide, distinctly constricted at base, lateral margins gradually divergent posteriad; disk uneven with distinct humeral impression, distinct sutural impression and rather faint postero-lateral impression; punctures fusiform and confluent, larger than those on pronotum, interstices between punctures microsculptured, much narrower than half the diameter of punctures.
Hind tarsi 0.70-0.75 times as long as hind tibiae, tarsomeres IV strongly bilobed. Abdomen cylindrical; paratergites very narrow and smooth, present only in segment III, segments IV-VI with tergites and sternites entirely fused and traces of paratergites present only at base of each segment, posterior margin of tergite VII with indistinct palisade fringe; punctures round, dense at the base of each tergite, gradually becoming smaller posteriad, interstices smooth.
Distribution. Jiangxi Province: Wugong Shan (China). Diagnoses. Stenus wugongshanus resembles S. huangganmontium Puthz, 2003 (Wuyishan, Jiangxi Province) in most aspects, but may be distinguished by the lack of paratergites on segments IV and V, which are present in S. huangganmontium.
Etymology. The specific name is derived from "Wugongshan", the type locality of this species. Brachypterous. Body blackish, each elytron with an orange marking near lateral margin, this marking about 2/3 as long and about 1/2 as broad as the respective elytron; antennae reddish yellow, club infuscate; maxillary palpi and legs reddish yellow; clypeus black, labrum brown, moderately densely pubescent. Paraglossae oval.
Head 1.08-1.12 times as wide as elytra; interocular area with two deep longitudinal furrows, median portion convex, not reaching level of inner eye margins, with a broad impunctate line along midline; punctures round to fusiform, larger and sparser in median area than near inner margins of eyes; diameter of large punctures about as wide as middle of 2nd antennal segment in cross section, interstices smooth, varying from narrower to slightly broader than half the diameter of punctures. Antennae, when reflexed, slightly extending beyond posterior margin of pronotum, antennomeres III-VIII segments distinctly narrower than II; IX-XI gradually broadened, forming loose club; relative length of segments from base to apex as 11.5: 7.5: 20.0: 10.5: 10.5: 8.5: 7.0: 5.0: 6.5: 6.0: 8.0. Pronotum 1.01-1.04 times as long as wide, widest a little before middle and constricted at base; with shallow median longitudinal furrow of about half the length of pronotum; punctures round, some of them confluent, variable in size, diameter of large punctures much larger than middle of 2nd antennal segment in cross section, interstices smooth, distinctly narrower than half the diameter of punctures.
Elytra 0.92-1.02 times as long as wide; distinctly constricted at base, lateral margins gradually divergent posteriad; disk uneven with distinct humeral impression and faint sutural impression; punctures similar to those of pronotum, interstices smooth, narrower than half the diameter of punctures.
Hind tarsi 0.72-0.74 times as long as hind tibiae, tarsomeres IV strongly bilobed. Abdomen cylindrical; paratergites very narrow and punctate, present only in segment III, segments IV-VI with tergites and sternites entirely fused and traces of paratergites present only at base of each segment, posterior margin of tergite VII with indistinct palisade fringe; punctures round, gradually becoming smaller posteriad, interstices smooth, varying from narrower to broader than diameter of punctures.
Etymology. The specific name is derived from "Mingyueshan", the type locality of this species. The new species is similar to S. mingyueshanus sp. n. in most respects, but different in the following characters: head 1.08-1.12 times as wide as elytra; frons with interstices smooth, varying from narrower to slightly broader than half the diameter  of punctures; relative length of antennal segments from base to apex as 9.5: 7.0: 18.5: 10.5: 8.5: 8.0: 6.5: 4.0: 6.0: 6.0: 7.0. Pronotum 1.08-1.13 times as long as wide; median longitudinal furrow shallow of about 2/5 the length of pronotum, punctures round and partly confluent, variable in size, diameter of large punctures slightly larger than middle of 2nd antennal segment in cross section; interstices smooth, distinctly narrower than half the diameter of punctures. Elytra 1.02-1.03 times as long as wide; size of punctures similar to those of pronotum, interstices partly with faint reticulation, somewhat narrower than half the diameter of punctures. Hind tarsi 0.77-0.80 times as long as hind tibiae. Male. Sternite VII with shallow emargination in the middle of posterior margin, sternite VIII (Fig. 28) with a circular emargination in the middle of posterior margin; sternite IX (Fig. 29) with long and acute apicolateral projections, posterior margin serrate and nearly straight; tergite X ( Fig. 30) with posterior margin broadly rounded. Aedeagus (Figs 31,32) with median lobe subparallel-sided in basal portion and broadening in apical half, apical margin truncate with a median projection, explusion hooks