Description of a new species of the genus Tribasodites Jeannel (Coleoptera, Staphylinidae, Pselaphinae) from East China with a key to world species

Abstract A remarkable new species of the genus Tribasodites, 1960, Tribasodites spinacaritus sp. n. is described and illustrated from Zhejiang Province, East China. A key to world species of the genus is provided. Systematic position of the new taxon is discussed.


Introduction
Th e genus Tribasodites was erected by Jeannel (1960) to accommodate two new species, T. antennalis and T. frontalis, both described from North India. Twenty-six years later, Nomura (1986) added a third species to the genus, T. picticornis collected in a colony of Paratrechina fl avipes (Smith) in Japan. Afterwards, Nomura (2000) listed eight species of Tribasodites based on the materials collected from Yunnan, but without specifi c name and description. Th en, Nomura (2007aNomura ( , 2007b transferred two species Batrisodes semipunctatus Raff ray, 1912 (Taiwan) and Batrisodes coiff aiti Jeannel, 1958 (Japan) to Tribasodites. So far, fi ve species of the genus have been known in the world.
Th e genus Tribasodites can be readily distinguished from its allies by a combination of the following characters: 1) male with sexually modifi ed head or antenna; 2) pronotum with a pair of spines or denticles on lateral sides, disc with a median longitudinal sulcus; 3) elytra each with three basal foveae; 4) male metatrochanter spinulate or simple; 5) the fi rst visible tergite (morphologically tergite IV) weakly concave near base, paratergites reduced to a pair of triangular plates demarcated by lateral carinae; 6) aedeagus asymmetrical, usually with a dorsal apophysis well-developed to totally reduced or absent.
During studies on the Chinese Tribasodites, some specimens were collected during a short expedition to Tiantongshan Mountain, Zhejiang Province, East China. Th e examination of the material revealed a remarkable species which is unknown to science.
Th e purpose of the present paper is to describe this new species under the name of Tribasodites spinacaritus sp. n., and to provide a key to all known species. Th e systematic position of the new species is also discussed.

Material and methods
Specimens were collected from decaying leaf litter of the forest fl oor by sifting and were killed with ethyl acetate and then dried. Dissections were made in 75% ethanol; genitalia and small parts were mounted in Euparal on plastic slides that were placed on the same pin with the specimens. Photos of habitus were taken by a Canon EOS 40D Camera mounted with an MP-E 65 mm Macro Photo Lens; photos of dissected parts were taken by a Canon G9 camera mounted on an Olympus CX21 microscope; line drawings were made by Adobe Illustrator CS2.  1). Reddish brown, maxillary palpi and tarsi lighter. Head ( Fig. 3) slightly wider than long, nearly triangular, covered with short hair on dorsal surface. Clypeus arcuate on anterior margin. Labrum (Fig. 5) longer than wide, with rows of long setae anterolaterally, anteromedian margin with four minute specialized setae. Mandible (Figs 6-7) with one large apical tooth and much smaller subapical tooth and row of median teeth on cutting edge; outer margin with long seta in apical one-third. Maxillary palpus ( Fig. 8) with palpomere I minute, II pedunculate with anterior third broadened, III nearly triangular, IV predominately large, nearly fusiform. Labium ( Fig. 9) slightly wider than long, rounded laterally, labial palpus composed of large basal segment and setae-like terminal segments; lateral lobe setose. Frons depressed between antennal tubercles. Vertex convex, with one pair of vertexal foveae connected by short U-shaped carina and with median keel. Eyes large and prominent, situated in basal twofi fths of head length, not emarginated, multifaceted, each composed of about 55 facets. Postgenae nearly rounded, with pair of lateral carinae extended to antennal tubercles. Gular area slightly depressed; gular foveae merged into single pit. Gular carina present. Antenna long and elongate, scape large, about 1.5 times as long as wide. Pedicle much smaller than scape, subcylindrical; antennomeres III-VIII each wider than long, transverse; club three-segmented with antennomeres IX-XI (Fig. 4) modifi ed, roughly granulated. X about twice as wide as and 1.5 times as long as VIII, nearly triangular, X slightly longer than wide, inner side strongly concaved, with several short and thick setae; XI the largest, widest in the middle, inner antebasal part strongly protuberant. Pronotum (Fig. 10) wider than long, lateral sides each with one median spine; with one pair of lateral and one pair of discal longitudinal sulci, one pair of antebasal spines near basal margin of pronotum, one pair of lateral antebasal foveae and two pairs of basolateral foveae distinct. Elytra (Fig. 17) convex, longer than wide, narrowed toward base. Each tri-foveate; discal stria extended to half of elytral length; sutural stria present. Metathoracic wings (Fig. 11) fully developed, widest at middle, gradually narrowed from middle toward Legs normal in structure. Mesotibia (Figs 12-13) with apical protuberance. Metatrochanter (Fig. 14) not spinose.
Etymology. Th e specifi c name refers to the metatrochanter without any spine or protuberance.
Relationship. Th e male genitalia of the new species is somewhat similar to that of Batrisodes or some species of Batrisus genus-group, and the male spine on the hind trochanter is absent in the new species, which makes the new species looks similar to Batrisodes in some male sexual characters. But it is still quite diff erent from Batrisodes. Th e new species is placed in Tribasodites because of the following reasons: 1) the prothorax of the new species has basic characters (spinulate lateral margins) of the Tribasodes genus-group, which never occurs in the Batrisodes belonging to Batrisus genus-group (both genus-groups were defi ned by Nomura and Idris 2003), 2) its male genitalia is strictly asymmetrical, which does not match the symmetrical male genitalia of Batrisodes.
Th e new species is most close related to T. picticornis and T. antennalis by relatively large body size and sexually modifi ed antennal club. T. spinacaritus can be readily distinguished by the absence of metatrochanteral spine on posterior margin and simple structure of aedeagus, while all the other species have spinulate metatrochanter and aedeagus with fully-developed dorsal apophysis. Eyes very small, less than 40 facets; antennomere IX clearly larger than X in male, with a conical protuberance on inner side, slightly smaller than X and symmetrical in female; pronotum without lateral process, but with a pair of small antebasal denticles; each protibia with a large denticle on inner side near the middle in male .......T. coiff aiti (Jeannel, 1958)  -Eyes developed, more than 50 facets; antennomere IX smaller than X in male, X asymmetrical in male, symmetrical and subglobose in female; pronotum with a pair of large lateral processes and with a pair of antebasal denticles; protibia slender and simple in both sexes .