Taxonomy of the genus Metolinus Cameron (Coleoptera, Staphylinidae, Staphylininae, Xantholinini) from China with description of three new species

Abstract This paper studies the taxonomy of the genus Metolinus Cameron, 1920 (Coleoptera: Staphylinidae, Staphylininae, Xantholinini) from China and describes three new species: Metolinus xizangensis sp. n. from Xizang (Tibet), Metolinus emarginatus sp. n. fromSichuan, and Metolinus binarius sp. n. from Yunnan. The Chinese fauna of the genus is thus increased to 8 species in total. A key to eight Chinese species is provided. Female genital segments and other important morphological characters are illustrated in line drawings for the new species as well as Metolinus shanicus Bordoni, 2002 and Metolinus gardneri (Cameron, 1945). The text also provides color plates with habitus photographs and a map to show the species’ geographical distribution pattern. The type specimens of the new species are deposited in Institute of Zoology, the Chinese Academy of Sciences (IZ-CAS).


Materials and methods
Specimens were relaxed in warm water (60 ºC) for about 5−8 hours, then cleared in 10% KOH for 5 minutes, and transferred in 75% alcohol. Cleared specimens were dissected to observe morphological details of mouthparts, abdominal segments VIII and sexual genital segments and the aedeagus. After examination, the body parts were stored permanently in glycerin for future studies. Observations and drawings were done under a compound microscope (ZEISS Stemi 2000-C). The specimens used in this study, including the types of the new species, are deposited in the Institute of Zoology, the Chinese Academy of Sciences (IZ-CAS).
In describing morphological features, we followed Smetana (1982), Naomi (1990), Smetana and Davies (2000), , Gusarov (2002) and Solodovnikov and Newton (2005). In addition, schematic line drawings were employed to avoid confusions in describing and measuring of some important body parts and diagnosing important taxonomic characters . Measurements were done with the aid of an eyepiece micrometer under the compound microscope ZEISS Stemi 2000-C (Germany) and were given in millimeter (mm) in the text. The following abbreviations were used throughout the paper:

HL
head length (from apex of epistoma to neck constriction); HW head width (maximal, including eyes); PL pronotum length (along mid line);         PW pronotum width (maximal); EL elytral length (from acute humerus to most distal apical margin; best taken from lateral view of the elytron); EW combined width of both elytra (maximal, when elytra closed along suture).
Color photographs were captured with a Nikon D300 and the final deep focus images were created with the stacking software Helicon Focus 3.10. The species distribution database was compiled with Microsoft Excel and is based on the data of published records as well as label data of available specimens. The distribution map was produced with the aid of ArcGIS 8.3.

Key to species of the genus
Head ( Fig. 10-1A). Subrectangular (HL to HW ratio 1.3), tempora (behind eyes) slightly widened posteriorly, posterior angles rounded. Dorsal integument shiny, with extensive microsculpture composed of a mixture of transverse microstriae and polygonal reticulum, and with sparse, scattered with setiferous punctures of medium size, distance between punctures ca. 2 puncture diameters. With pair of frontal puncture on epistoma, 2 antennal punctures near antennal insertion, ocular puncture near medial  margin of eye (ca. 3-4 puncture diameters to eye), temporal puncture at posterior 1/5 and occipital puncture at lateral 1/3; deflexed portion of tempora with same setiferous punctures and microstriae as on dorsal integument. Frontal furrows superficial and short, not longer than 1/2 of eye length. Ocular furrows of medium length, equal to eye length. Eye of medium size, nearly 1/3 of temple length (eye: temple = 0.23:0.68 mm), slightly protruding laterad. Epistoma protruding forwards, anterior margin subtruncated, dorsally flat and broad, as wide as 1/2 of eye length. Distance between antennal insertions ca. 0.32 mm, obviously wider than that from antenna to eye (ca. 0.26 mm). Ventral integument shiny, with polygonal reticulum, and with setiferous punctures as on dorsal integument, but obviously denser laterad. Mentum with a pair of setae inserted at anterior angle in addition to other irregularly scattered setae, submentum with 2 pairs of setae. Gular sutures fused at middle, and not separated at base of occiput. Gular plate devoid of punctures, with distinct transverse microstriae.
Mouthparts. Labrum transverse and V-shaped bilobed, two lateral teeth subtruncated on anterior margin. Mandibles falciform, left one with two teeth on medial edge. Maxillary palpus elongate, with 3 rd segment longest, last slender and aciculate. Labial palpus distinctly slender, with 2 nd longest, last slender and aciculate.
Abdomen. Cylindrical, broadest at segment VI. Terga III-VII shiny, entire surface covered with distinct transverse microstriae, sparsely scattered with dot-like setiferous punctures, but denser laterobasally; each tergite with impunctate basal impression bearing more obvious transverse microstriae. All abdominal sterna shiny, with microstriae and setiferous punctures as those on terga.
Male. Tergite VIII entirely covered with setiferous punctures, except a narrow medial longitudinal impunctate band; posterior margins of tergite VIII and sternite VIII both arcuately protruding backwards (Fig. 10A, B). Tergite of genital segment symmetrical and small, with sharp base and subtruncated apex ( Fig. 10C), in situ broadly exposed between pleurites. Pleurites of genital segment symmetrical, connected mediobasally. Sternite asymmetrical, with rounded base and more angular left side ( Distribution. China (Xizang). Etymology. The specific epithet is the Chinese name (Pin-Yin) of the type locality.
Remarks. This species could be distinguished from its congeners by microsculpture on head, the shape of the male genital segment (Fig. 10C, D) and the internal sac of the aedeagus (Fig. 10G).   Body medium sized and nearly compressed. Body entirely dark brown, except each apical 1/3 of abdominal segment lighter. Legs dark brown, tarsi lighter. Antennae, maxillary palpi and labial palpi light brown.

Metolinus emarginatus
Head . Subquadrate (HL to HW ratio 1.1), tempora (behind eyes) widened posteriorly, posterior angles rounded. Dorsal integument shiny, extensively covered with distinct transverse microstriae, and with sparse, scattered setiferous punctures of medium size, distance between punctures ca. 3 puncture diameters. With pair of frontal puncture on epistoma, 2 antennal punctures near antennal insertion, ocular puncture near medial margin of eye (ca. 3-4 puncture diameters from eye), temporal puncture at posterior 1/5 and occipital puncture at lateral 1/3; deflexed portion of tempora with same setiferous punctures and microstriae as on dorsal integument. Frontal furrows parallel and of medium length, longer than 1/2 of eye length. Ocular furrows deep and long, over eye length. Eye medium sized, nearly 1/3 of temple length (eye: temple =0.18:0.53 mm), slightly protruding laterad. Epistoma not protruding, anterior margin subtruncated, dorsally flat and broad, over 1/2 of eye length. Distance between antennal insertions ca. 0.23 mm, subequal to that from antenna to eyes (ca. 0.26mm). Ventral integument shiny, with same microstriae and setiferous punctures as on dorsal integument. Mentum with three pairs of setae inserted at each anterior angle in addition to other irregularly scattered setae, submentum with four pairs of setae. Gular sutures fused at middle, but separated at base of occiput. Gular plate devoid of punctures, but with distinct transverse microstriae.
Mouthparts. Labrum short and U-shaped bilobed, two subtruncated teeth on anterior margin. Mandibles falciform, left one with two teeth on medial edge. Maxillary palpus elongate, with 3 rd segment longest, last slender and aciculate. Labial palpus distinctly slender, with 2 nd longest, last slender and aciculate.
Legs. First four segments of protarsi obviously dilated, heart shaped, bearing extremely dense clothing of white fine hairs ventrally, last tarsomere as long as III-IV combined. Last segment of both meso-and metatarsi longer than that of protarsi and about equal to length of II-IV combined. Tibiae with apical ctenidium, only protibia with 2-3 rows of subapical ctenidia.
Abdomen. Cylindrical, broadest at segment VI. Terga III-VII shiny, entire surface covered with distinct transverse microstriae, with sparse, scattered, tiny setiferous punctures; each tergite with impunctate basal impression bearing more obvious transverse microstriae. All abdominal sterna shiny, with microstriae and setiferous punctures as those on terga.
Female. Posterior margin of tergite VIII and sternite VIII distinctly arcuate backwards. Genital segment (Fig. 11-1C) small, ca. 0.50 mm long. Sternite with subtruncated base. In addition, with some membranous structures attached to base of genital segment.
Distribution. China (Sichuan). Etymology. The specific epithet is the Latin word emarginatus (emarginate) and refers to the shape of anterior margin of the epistoma.
Remarks. Although the shape of the median lobe of the aedeagus seems similar to that of M. yunnanus M. loebli Bordoni 2002, the species may be distinguished by the longer parameres (Fig. 11E), different shape and composition of the internal sac (Fig. 11G), and by the tergite and sternite of the genital segment ( Fig  11A, B). Body medium sized and nearly compressed. Body entirely dark brown. Legs dark brown, tarsi lighter. Antennae, maxillary palpi and labial palpi light brown.

Metolinus binarius
Head (Fig. 12-1A). Subrectangular (HL to HW ratio 1.2), tempora (behind eyes) obviously widened posteriorly, posterior angles rounded. Dorsal integument shiny, extensively covered with distinct transverse microstriae, and sparse, scattered setiferous punctures of medium size, distance between punctures ca. 5-6 puncture diameters. With pair of frontal puncture on epistoma, 2 antennal punctures near antennal insertion, ocular puncture near medial margin of eye (ca. 3-4 puncture diameters from eye), temporal puncture at posterior 1/5 and occipital puncture at lateral 1/3; deflexed portion of tempora with same setiferous punctures and microstriae as on dorsal integument. Frontal furrows superficial and short, slightly shorter than 1/2 of eye length. Ocular furrows of medium length, subequal to 1/2 of eye length. Eye of relatively large size, longer than 1/2 temporal length (eye: temple =0.18:0.29 mm), distinctly protruding laterad. Epistoma protruding forwards, anterior margin subtruncated, dorsally flat and broad, as wide as 1/2 of eye length. Distance between antennal insertions ca. 0.20 mm, obviously wider than distance from antenna to eyes (ca. 0.09 mm). Ventral integument shiny, with same microstriae and setiferous punctures as on dorsal integument. Mentum with a pair of setae inserted at each anterior angle in addition to other irregularly scattered setae, submentum with 2 pairs of setae. Gular sutures fused at middle, and not separated at base of occiput. Gular plate devoid of punctures, but with distinct transverse microstriae.
Legs. First four segments of protarsi obviously dilated, heart shaped, bearing extremely dense clothing of white fine hairs ventrally, last tarsomere as long as III-IV combined. Last segment of both meso-and metatarsi longer than that of protarsi and about equal to length of II-IV combined. Tibiae with apical ctenidium, only protibia with 2-3 rows of subapical ctenidia.
Abdomen. Cylindrical, broadest at segment VI. Terga III-VII shiny, entire surface covered with distinct transverse microstriae, with sparse, scattered, tiny setiferous punctures, but denser laterobasally; each tergite with impunctate basal impression bearing more obvious transverse microstriae. All abdominal sterna shiny, with microstriae and setiferous punctures as those on terga.
Distribution. China (Yunnan). Etymology. The specific epithet is derived from the Latin word binarius and refers to the pair of spines on the apical portion of the internal sac.
Remarks. Although the large eyes and the number of punctures on the pronotum are similar to M. schulzvocki Bordoni, 2003 andM. heuresilogus Bordoni, 2002, it may be distinguished by the combined characters of the male genital segment (Fig. 12C, D) and the aedeagus (Fig. 12-1D; Fig. 12E-G).
Head (Fig. 13-1A). Subquadrate (HL to HW ratio 1.1), tempora (behind eyes) subparallel or slightly widened posteriorly, posterior angles rounded. Dorsal integument shiny, extensively covered with distinct transverse microstriae, and sparse, scattered setiferous punctures of medium size, distance between punctures ca. 4-5 puncture diameters. On each side symmetrically with frontal puncture on the epistoma, 2 antennal punctures near antennal insertion, ocular puncture near inner side of eye (ca. 3-4 puncture diameters from eye), temporal puncture at posterior 1/4 and occipital puncture at lateral 1/3; deflexed portion of tempora with same setiferous punctures and microstriae as on dorsal integument. Frontal furrows of medium length, ca. 2/3 of eye length, slightly curved and extending backward to same level of eye midlength. Ocular furrows of medium length, as long as eye length. Eye of medium size, nearly 1/3 of temple length (eye: temple =0.15:0.45 mm), and slightly protruding laterad. Epistoma protruding forwards, anterior margin subtruncated, dorsally flat and broad, as wide as 1/2 of eye length. Distance between antennal insertions ca. 0.23 mm, obviously wider than that from antenna to eyes (ca. 0.15 mm). Ventral integument shiny, with same microstriae and setiferous punctures as dorsal integument, except punctures deeper. Mentum with two pairs of setae inserted at anterior angles in addition to other irregularly scattered setae, submentum with 2 pairs of setae. Gular sutures fused at middle, not separated at base of occiput. Gular plate devoid of punctures, but with distinct transverse microstriae.
Mouthparts. Labrum transverse and V-shaped bilobed, with two subtruncated teeth on anterior margin. Mandibles falciform, left one with two teeth on medial edge. Maxillary palpus elongate, with 3 rd segment longest, last slender and aciculate. Labial palpus distinctly slender, with 2 nd longest, last slender and aciculate.
Legs. First four segments of protarsi obviously dilated, heart shaped, bearing extremely dense clothing of white fine hairs ventrally, last tarsomere as long as III-IV  combined. Last segment of meso-and metatarsi longer than that of protarsi and about equal to length of II-IV combined. Tibia with apical ctenidium, only protibia with 2-3 rows of subapical ctenidia.
Abdomen. Cylindrical, broadest at segment VI. Terga III-VII shiny, entire surface covered with distinct transverse microstriae, with sparse, scattered, round setiferous punctures, but denser laterobasally; each tergite with impunctate basal impression bearing more obvious transverse microstriae. All abdominal sterna shiny, with microstriae and setiferous punctures as those on terga.
Remarks. This species may be distinguished from its congeners by the bicolorous elytra, the unique internal sac of aedeagus (Fig. 13G) and genital segment (Fig. 13C,  D). However, the shape of the male tergite VIII of the specimens reported here slightly differs from the illustration given by Bordoni (2002: 374) which might reflect some degree of intraspecific variation. (Cameron, 1945) http://species-id.net/wiki/Metolinus_gardneri Fig. 14A-H; Fig. 14 Body small sized and nearly compressed. Head, pronotum, mesoscutellum and elytra entirely black. Abdomen dark brown, posterior margin of segment VII and VIII paler. Legs dark brown, tarsi lighter. Antennae brown except apical 1/2 of 11th segment yellowish. Maxillary palpi and labial palpi light brown.

Metolinus gardneri
Head (Fig. 14-1A). Subrectangular (HL to HW ratio 1.3), tempora slightly widened posteriorly, posterior angles rounded. Dorsal integument shiny, extensively covered with distinct transverse microstriae, and sparse, scattered setiferous punctures of medium size, distance between punctures ca. 3 puncture diameters. On each side symmetrically with frontal puncture on the epistoma, 2 antennal punctures near antennal insertion, ocular puncture near medial margin of eye (ca. 3-4 puncture diameters from eye), temporal puncture at posterior 1/5 and occipital puncture at lateral 1/3; deflexed portion of tempora with smaller setiferous punctures, and microstriae same as on dorsal integument. Frontal furrows superficial and short, shorter than 1/2 of eye length. Ocular furrows of medium length, subequal to eye length. Eye of medium size, slightly longer than 1/3 of temple length (eye: temple=0.18:0.42 mm), and slightly protruding laterad. Epistoma protruding forwards, anterior margin subtruncated, dorsally flat and broad, as wide as 1/2 of eye length. Distance between antennal insertions ca. 0.23 mm, obviously wider than distance from antenna to eyes (ca. 0.15 mm). Ventral integument shiny, with same microstriae and setiferous punctures as on dorsal integument. Mentum with two pairs of setae inserted at anterior angles in addition to other irregularly scattered setae, submentum with 3 pairs of setae. Gular sutures fused at middle, and separated at base of occiput. Gular plate devoid of punctures, but spread with distinct transverse microstriae.
Mouthparts. Labrum short and V-shaped bilobed, with two subtruncated teeth on anterior margin. Mandibles falciform, left with two teeth on medial edge. Maxillary palpus elongate, with 3 rd segment longest, last slender and aciculate. Labial palpus distinctly slender, with 2 nd longest, last slender and aciculate.
Legs. First four segments of protarsi obviously dilated, heart shaped, bearing extremely dense clothing of white fine hairs ventrally, last tarsomere as long as III-IV combined. Last segment of both meso-and metatarsi longer than that of protarsi and about equal to length of II-IV combined. Tibiae with apical ctenidium, only protibia with 2-3 of subapical ctenidia.
Abdomen. Cylindrical, broadest at segment VI. Terga III-VII shiny, entire surface covered with distinct transverse microstriae, with sparse, scattered, tiny setiferous punctures, but denser laterobasally; each tergite with impunctate basal impression bearing more obvious transverse microstriae. All abdominal sterna shiny, with microstriae and setiferous punctures as those on terga.
Remarks. This species may be distinguished from its congeners by the few number of admedian punctural row of pronotum, the unique internal sac of the aedeagus (Fig.  14G) and genital segment (Fig. 14C, D).