Five new species of the Stenus indubius group (Coleoptera, Staphylinidae) from China

Abstract Five new species of the Stenus indubius group from China are described: Stenus cangshanus sp. n. from Yunnan Province, Stenus hewenjiae sp. n. from Sichuan Province, Stenus taiyangshanus sp. n. from Guangdong Province, Stenus yinziweii sp. n. and Stenus zhaiyanbini sp. n. from Guizhou Province.Diagnostic characters are illustrated and a key to the species of this group from the Chinese mainland is provided.


Introduction
Stenus indubius group is a medium Asian group comprising 26 Japanese species (see Naomi 2006, also for a group definition) and ten Chinese species: S. guniujiangense Tang & Li, 2005 and S. paradecens Tang & Li, 2005 from Anhui Province, S. zhuxiaoyui Tang, 2008, S. pectorifossatus Tang, 2008and S. erlangshanus Tang, 2008 from Sichuan Province, S. hui Tang & Puthz, 2009 from Shaanxi Province, S. electristigma Puthz, 2011, S. shibatai Puthz, 2011, S. shibataianus Puthz, 2011and S. shibataiellus Puthz, 2011 All hitherto known members from the Chinese mainland of the group are brownish to blackish and brachypterous. In this paper, we describe five new species of the group collected in various mountainous areas in South China, three of them with orange spots on elytra, a character also present in Taiwanese species of this group Puthz (2011).

Material and methods
The specimens examined in this paper were collected by sifting leaf litters in forests and killed with ethyl acetate. For examination of the male genitalia, the last three abdominal segments were detached from the body after softening in hot water. The aedeagi, together with other dissected pieces, were mounted in Euparal (Chroma Gesellschaft Schmidt, Koengen, Germany) on plastic slides. Photos of sexual characters were taken with a Canon G7 camera attached to an Olympus SZX 16 stereoscope; habitus photos were taken with a Canon macro photo lens MP-E 65 mm attached to a Canon EOS40D camera.
The type specimens treated in this study are deposited in the following public and private collections:

NMB
Museum of Natural History Basel, Switzerland NSMT National Museum of Nature and Science, Tokyo SHNU Department of Biology, Shanghai Normal University, P. R Head 1.07-1.12 times as wide as elytra; interocular area with deep longitudinal furrows, median portion convex, slightly extending beyond the level of inner eye margins; punctures round, partly confluent, slightly larger and sparser on median area than those near inner margins of eyes, diameter of large punctures about as wide as apical cross section of antennal segment II; interstices faintly reticulated, much smaller than half the diameter of punctures except those along the midline of the convex median portion, which may be as wide as diameter of punctures. Antennae, when reflexed, extending a little before posterior margin of pronotum; relative length of antennal segments from base to apex as 12.0: 7.5: 16.5: 10: 11: 7.5: 8: 5: 5.5: 6: 7.5. Paraglossa oval.
Pronotum 1.05-1.09 times as long as wide; disk uneven, with distinct median longitudinal furrow, two impressions in anterior half, transverse impression in the middle, and two impressions in posterior half; punctures rugose and confluent, of similar size as those of head; interstices reticulated, more or less smaller than half the diameter of punctures except those at the bottom of longitudinal furrow, which could be larger.
Elytra 0.89-0.93 times as long as wide, distinctly constricted at base; lateral margins, with slight concavity at about half, gently divergent posteriad; disk moderately uneven with distinct longitudinal humeral impression, distinct postero-lateral impression and long sutural impression, suture moderately convex; punctation and interstices similar to those of pronotum.
Legs with hind tarsi 0.72 times as long as hind tibiae, tarsomeres IV distinctly bilobed. Abdomen cylindrical; distinct paratergites absent, but rudimentary lateral border present, tergites and sternites distinctly split at about posterior eighth; posterior margin of tergite VII with palisade fringe; punctures of abdominal tergites III-VIII round to elliptic, gradually becoming smaller posteriad; interstices smaller than half the diameter of punctures, with relatively faint microsculpture on tergites III-VII and distinct reticulation on tergites VIII-X.
Male. Sternite VII with inconspicuous emargination at middle of posterior margin and a shallow impression before it; sternite VIII ( Female. Abdomen broader than that in male; sternite VIII ( Fig. 18) inconspicuously prominent at middle of posterior margin; tergite X ( Fig. 19) slightly broader than that of male; sclerotized spermatheca as in Figs 20, 21.
Distribution. China (Yunnan Province: Mt. Cang Shan). Diagnoses. In general facies and body size, the new species resembles S. hui Tang, 2009, S. pectorifossatus Tang, 2008and S. erlangshanus Tang, 2008, but it may be distinguished by the characters listed in the key, particularly by the different sexual characters.
Etymology. The specific name is derived from "Cangshan", the type locality of this species. Tang  Head 1.18-1.24 times as wide as elytra; interocular area with deep longitudinal furrows, median portion convex, slightly extending beyond the level of inner eye margins; punctures round, mostly well delimited, slightly larger and sparser on median area than those near inner margins of eyes, diameter of large puncture about as wide as basal cross section of antennal segment II; interstices faintly reticulated, smaller than half the diameter of punctures except those along the midline of convex median portion and on the bottom of lateral furrows, which could be more or less larger. Antennae, when reflexed, extending a little before posterior margin of pronotum; relative length of antennal segments from base to apex as 10: 7.5: 15.5: 9.5: 9: 6: 6: 4: 4.5: 5: 7.5. Paraglossa oval.

Stenus hewenjiae
Pronotum 1.05-1.13 times as long as wide; disk uneven, with distinct short median longitudinal furrow, transverse impression each in anterior half and in the middle, and two indistinct impressions in posterior half; punctures of similar size as those of head, rugose and confluent, forming vorticose rugae surrounding the longitudinal furrow; interstices indistinctly microsculptured, more or less smaller than half the diameter of punctures except those on the bottom of longitudinal furrow, which may be larger.
Elytra 0.92-0.97 times as long as wide, distinctly constricted at base, lateral margins with slight concavity in the middle, gently divergent posteriad; disk uneven with long deep longitudinal humeral impression and sutural impression, indistinct posterolateral impression, suture strongly convex; punctation and interstices similar to those of pronotum.
Hind tarsi 0.69 times as long as hind tibiae, tarsomeres IV distinctly bilobed. Abdomen cylindrical; distinct paratergites absent, but rudimentary lateral border present, tergites and sternites distinctly split at about posterior eighth; tergite VII with palisade fringe; punctures on abdominal tergites III-VIII round to elliptic, gradually becoming smaller posteriad; interstices on tergites III-VI faintly microsculptured and on tergites VIII-X distinctly microsculptured.
Female. Abdomen broader than that in male; sternite VIII ( Fig. 29) inconspicuously prominent at middle of posterior margin; tergite X ( Fig. 30)  Etymology. This species is named in honor of Ms. Wen-Jian He, wife of the first author, who collected some of the specimens of the new species. Head 1.17-1.23 times as wide as elytra; interocular area with deep longitudinal furrows, median portion convex, slightly extending beyond the level of inner eye margins; punctures round, partly confluent, slightly larger and sparser on median area than those near inner margins of eyes, diameter of large punctures about as wide as basal cross section of antennal segment II; interstices faintly reticulated, much smaller than half the diameter of punctures except those on vertex and behind basiantennal tubercles, which may be much larger. Antennae, when reflexed, extending a little after posterior margin of pronotum; relative length of antennal segments from base to apex as 11: 7: 16: 8.5: 10: 7.5: 7: 5: 5.5: 5.5: 9. Paraglossa oval. Pronotum 1.10-1.12 times as long as wide; disk slightly uneven, with distinct median longitudinal furrow, two indistinct impressions in anterior half, indistinct transverse impression in the middle, and two indistinct impressions in posterior half; punctures moderately rugose and confluent, of similar size as those of head; interstices, especially those on the bottom of median longitudinal furrow distinctly reticulated, more or less smaller than half the diameter of punctures except those on the bottom of median longitudinal furrow, which may be larger.
Elytra 0.95-1.01 times as long as wide, distinctly constricted at base, lateral margins with slight concavity at about half, gently divergent posteriad; disk slightly uneven with shallow longitudinal humeral impression, shallow postero-lateral impression and shallow sutural impression, suture moderately convex; punctation and interstices similar to those of pronotum.
Hind tarsi 0.7 times as long as hind tibiae, tarsomeres IV distinctly bilobed. Abdomen cylindrical; distinct paratergites absent, but rudimentary lateral border present; tergite VII with palisade fringe; punctures on abdominal tergites III-VIII round to elliptic, gradually becoming smaller posteriad; interstices smaller to little larger than half the diameter of punctures, with relatively faint microsculpture throughout abdominal tergites.
Female. Abdomen broader than that in male; sternite VIII inconspicuously prominent at the middle of posterior margin; tergite X slightly emarginated at posterior margin; sclerotized spermatheca can't be observed in immature female and thus it can't be illustrated here.
Diagnoses. This new species can be easily distinguished from related species by vague undelimited elytral spots and small body size.
Etymology. The specific name is derived from "Taiyangshan", the type locality of this species. Description. Brachypterous; body blackish, anterior margin of labrum, antennae, maxillary palpi and legs yellowish brown, each elytron with a large elongate orange spot, which is 3/5 to 4/5 as long as and 1/2 to 2/3 as broad as the respective elytron.
BL Head 1.10-1.20 times as wide as elytra; interocular area with deep longitudinal furrows, median portion convex, slightly extending beyond the level of inner eye margins; punctures round, partly confluent, slightly larger and sparser on median area than those near inner margins of eyes, diameter of large puncture about as wide as apical cross section of antennal segment II; interstices faintly reticulated, much smaller than half the diameter of punctures except those along the midline of convex median portion, which may be larger. Antennae, when reflexed, extending a little after posterior margin of pronotum; relative length of antennal segments from base to apex as 12: 7: 21: 10.5: 10.5: 8.5: 8.5: 6: 6: 6.5: 9. Paraglossa oval. Pronotum 1.10-1.16 times as long as wide; disk moderately uneven, with distinct median longitudinal furrow, two shallow impressions in anterior half, shallow transverse impression in the middle, and two shallow impressions in posterior half; punctures slightly rugose and partially confluent, slightly larger than those on head; interstices, especially those on the bottom of median longitudinal furrow distinctly reticulated, more or less smaller than half the diameter of punctures except those on the bottom of median longitudinal furrow which may be much larger.
Elytra 0.95-0.98 times as long as wide, distinctly constricted at base, lateral margins with slight concavity at about half, gently divergent posteriad; disk uneven with distinct longitudinal humeral impression, distinct postero-lateral impression and long, deep sutural impression, suture convex; punctation and interstices similar to those of pronotum.
Hind tarsi 0.72 times as long as hind tibiae, tarsomeres IV distinctly bilobed. Abdomen cylindrical; distinct paratergites absent, but rudimentary lateral border present, tergites and sternites split apically; tergite VII with palisade fringe; punctures on abdominal tergites III-VIII round to elliptic, gradually becoming smaller posteriad; interstices smaller than half the diameter of punctures, with relatively faint reticulation on tergites III-VII and distinct reticulation on tergites VIII-X.
Diagnoses. This new species closely resembles S. zhaiyanbini sp. n. and both of them live in the same nature reserve, but it may be distinguished from the latter species by larger size of the elytral marks and different sexual characters.
Etymology. This species is named in honor of Mr. Zi-Wei Yin, collector of the new species.  Tang  Description. Brachypterous; body blackish, anterior margin of labrum, antennae, maxillary palpi and legs yellowish brown, each elytron with a large oval orange spot, which is 1/3 to 1/2 as long as and 1/3 to 2/5 as broad as the respective elytron. Head 1.14-1.21 times as wide as elytra; interocular area with deep longitudinal furrows, median portion convex, reaching the level of inner eye margins; punctures round, partly confluent, slightly larger and sparser on median area than those near inner margins of eyes, diameter of large punctures about as wide as apical cross section of antennal segment II; interstices hardly reticulated, much smaller than half the diameter of punctures except those along the midline of convex median portion, which may be larger. Antennae, when reflexed, extending a little after posterior margin of pronotum; relative length of segments from base to apex as 11.5: 7.5: 22: 12.5: 11: 9: 8.5: 6.5: 6.5: 6.5: 7.5. Paraglossa oval.

Stenus zhaiyanbini
Pronotum 1.10-1.15 times as long as wide; disk uneven, with distinct median longitudinal furrow, two impressions in anterior half, transverse impression in about the middle, and two impressions in posterior half; punctures slightly rugose and partially confluent, slightly larger than those on head; interstices faintly reticulated, more or less smaller than half the diameter of punctures.
Elytra 0.94-1.01 times as long as wide, distinctly constricted at base, lateral margins, with slight concavity at about half, gently divergent posteriad; disk uneven with shallow longitudinal humeral impression, shallow postero-lateral impression and long, deep sutural impression, suture convex; punctation little larger than that of pronotum and interstices clearly microsculptured.
Hind tarsi 0.69 times as long as hind tibiae, tarsomeres IV distinctly bilobed. Abdomen cylindrical; distinct paratergites absent, but rudimentary lateral border present, tergites and sternites split apically; tergite VII with palisade fringe; punctures on abdominal tergites III-VIII round to elliptic, gradually becoming smaller posteriad; interstices smaller than half the diameter of punctures, with relatively faint reticulation on tergites III-VII and distinct reticulation on tergites VIII-X.