Notes on the Stenus cirrus group, with description of two new species from China (Coleoptera, Staphylinidae)

Abstract Two new species, Stenus zhangdinghengi sp. n., Stenus maoershanus sp. n.,of the Stenus cirrus group are described from South China, Guangxi Province. The male of Stenus fellowesi Puthz, 2003 and the female of Stenus huanghaoi Tang & Li, 2008 were discovered for the first time. Their diagnostic characters are illustrated and a key to the Chinese species of the Stenus cirrus group is provided.


Introduction
The Stenus cirrus group is a large group of the genus with 57 species worldwide and 24 species in China. The members of the group are characterized by the presence of long and erect setae on the abdomen. A detailed group definition was given by Puthz (2009).
Among the specimens we collected from China recently, the male of S. fellowesi Puthz, 2003, described from Hainan Province, and the female of S. huanghaoi Tang & Li, 2008, described from Guangdong Province, were discovered for the first time. Two species of the Stenus cirrus group collected from Guangxi Province are recognized as new and described for the first time.

Material and methods
The specimens examined in this paper were collected by sifting leaf litter in forests. For an 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 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 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:  9) impressed in posteromedian portion with emargination along posterior margin of impression, impression densely setose; sternite VIII ( Fig. 10) with a triangular emargination at middle of posterior margin, length of the emargination about 1/ 5 of total length along the midline; sternite IX ( Fig. 11) with long and slightly acute apicolateral projections, posterior margin nearly straight; tergite X ( Fig.  12) with posterior margin truncate. Median lobe of aedeagus ( Fig. 13) broad near base and tapering apicad, apex of median lobe (Fig. 14) forming an acute projection with two pairs of short setae; parameres (Fig. 14) slightly longer than median lobe, swollen at apex, each with about 14 to 15 setae on apico-internal margins.
Variation. The duct of the spermatheca may be folded to different degrees .
Distribution. China (Hainan Province: Diaoluoshan). Tang   Notes. In the original description, the elytral mark of the species was described as obsolete. In fact, there is an indistinct elongate orange mark in the lateral portion of each elytron (Fig. 3).

Stenus huanghaoi
Distribution. China (Guangdong Province: Nanling). Brachypterous; body brownish except for the blackish head, anterior margin of labrum, antennae, maxillary palpi and legs yellowish brown, each elytron with an elongate ill-defined orange mark near lateral side, this mark 1/3 to 1/2 as long and about 1/3 to 2/5 as broad as the respective elytron.

Stenus zhangdinghengi
Head 1.16-1.21 times as wide as elytra; interocular area with two broad longitudinal furrows, median portion convex dorsally, not reaching level of inner eye margins; punctation round and slightly confluent, uniform except for several large punctures at posterior part of median portion; diameter of large punctures about as wide as antennal segment II in cross-section, interstices between punc- tures smooth, mostly narrower than half the diameter of punctures, those along midline much wider, forming a broad impunctate line. Relative length of antennal segments from base to apex 12: 9: 20: 11: 10.5: 10.5: 9: 6.5: 7: 8: 10.5. Paraglossae oval.
Pronotum 1.05-1.09 times as long as wide, 0.81-0.88 times as wide as elytra; disk with shallow median longitudinal furrow about 1/2 the length of pronotum; punctures round and moderately confluent, smaller in size than largest punctures on head, interstices smooth, narrower than half the diameter of punctures.
Elytra 0.96-0.98 times as long as wide, distinctly constricted at base, lateral margins gently divergent posteriad; disk almost even; punctures round to elliptic, uniform, slightly coarser than those of pronotum, interstices smooth, narrower than half the diameter of punctures.
Legs with hind tarsi 0.72-0.78 times as long as hind tibiae, tarsomere IV strongly bilobed. Abdomen cylindrical; paratergites very narrow and smooth, present only at abdominal segment III, tergite VII with indistinct palisade fringe; punctation of tergite III-VIII sparse and shallow, gradually becoming finer posteriad, interstices smooth, varying from narrower to much wider than diameter of punctures.
Male. Sternite VII with shallow emargination at middle of posterior margin and a depression before it; sternite VIII ( Diagnosis. The new species resembles S. huanghaoi Tang & Li, 2008, with which it shares the faint elytral marks, but it may be distinguished by the heterogeneous punctation of the frons (in S. huanghaoi always similar in size), the shallower pronotal punctation (especially in the median furrow) and smaller body size (in S. huanghaoi BL: 3.9-4.5 mm).
Etymology. This species is named in honor of Mr. Zhang Ding-Heng, administrator of the Huaping Nature Reserve, who provided help in various ways during our field work.
Biological notes. All the specimens were collected by sifting the leaves of bamboo and broad-leaved shrubs in a thick forest (Fig. 50). Brachypterous; body brownish black, head darker, anterior margin of labrum, antennae, maxillary palpi and legs yellowish brown, each elytron with a large elongate orange mark near lateral margin, this mark 4/5 as long as and about 3/5 as broad as the respective elytron.

Stenus maoershanus
Head 1.07-1.08 times as wide as elytra; interocular area with two broad longitudinal furrows, median portion convex, almost reaching the level of inner eye margins; punctures round, slightly larger and sparser in median area than those near inner margins of eyes, diameter of large punctures as wide as apical cross section of antennal segment II, interstices between punctures smooth, mostly narrower than half the diameter of punctures, those along midline a little wider. Relative length of antennal segments from base to apex 15: 9: 24: 14: 12: 9.5: 9.5: 6.5: 7: 8: 10. Paraglossae oval.
Pronotum 1.04-1.05 times as long as wide, 0.80-0.81 times as wide as elytra; disk with distinct median longitudinal furrow, this furrow about half the length of pronotum; punctation round and confluent, similar to that of head, interstices smooth, much narrower than half the diameter of punctures except for those in median furrow, which may be wider.
Elytra 0.94-0.95 times as long as wide, distinctly constricted at base, lateral margins gently divergent posteriad; punctation similar to that of pronotum, but slightly coarser, interstices similar to those of pronotum.
Legs with hind tarsi 0.74-0.75 times as long as hind tibiae, tarsomere IV strongly bilobed. Abdomen cylindrical; paratergites very narrow and smooth, present only in abdominal segment III, posterior margin of tergite VII with indistinct palisade fringe; punctation of tergite III-VIII sparse and shallow, gradually becoming finer posteriad, interstices smooth, varying from narrower to much wider than diameter of punctures.
Female. Sternite VIII (Fig. 46) inconspicuously prominent at middle of posterior margin; tergite X ( Fig. 47) with posterior margin truncate and slightly emarginated at middle. Valvifers (Fig. 48) each with big apicolateral tooth; spermatheca strongly sclerotized (Fig. 49). Tang & Li, 2008 from Guangdong, but may be distinguished by the broader and deeper pronotal furrow with wider interstices, which may be as wide as diameter of punctures (in S. nanlingmotis smaller than half the diameter of punctures); the elytral marks are broader, about 3/5 as broad as the respective elytron (in S. nanlingmotis about 2/5 as broad as the respective elytron).

Diagnosis. The new species resembles S. nanlingmotis
Etymology. The specific name is derived from "Mao'ershan", the type locality of this species.
Biological notes. The female specimen was collected by sifting the leaves of bamboo and broad-leaved shrubs near the mountain summit, the male specimen was collected by beating grass along a drain exposed in sunshine. Elytra bicolored; pronotum and elytra with more strongly sculptured interstices. Spermatheca: Fig. 14