Notes on the genus Ismarus Haliday (Hymenoptera, Diapriidae) from China

Abstract The Chinese species of the genus Ismarus Haliday, 1835, are revised for the first time. Three new species from the Oriental region of China and belonging to Ismarus halidayi-group are described and illustrated: Ismarus longus sp. n., Ismarus nigritrochanter sp. n. and Ismarus parvicellus sp. n. Two species are newly reported for the Chinese fauna: Ismarus dorsiger (Haliday, 1831) and Ismarus halidayi Foerster, 1850. A key to the Chinese species of the genus is provided. The type specimens are deposited in the Hymenopteran Collection of South China Agricultural University, Guangzhou (SCAU).


Introduction
The small subfamily Ismarinae belongs to the family of Diapriidae and is characterized by the rather low insertion of antennae, the transverse head, the reduced notauli, the fore legs with a peculiar combing apparatus, the hind tibia with a false second spur and the carapace-like metasoma. The subfamily includes two genera: Ismarus Haliday, 1835 andSzelenyioprioides Szabó, 1974. The relationships between Ismarinae and the other subfamilies of the family Diapriidae have been discussed by Masner (1976). In total, the Ismarinae contains thirty species (twenty nine in Ismarus and one in Szelenyioprioides) described from the Palaearctic, Nearctic, Neotropical and Australian regions (Nixon 1957;Hellén 1964;Wall 1967a, b;Szabó 1974;Masner 1976;Johnson 1992;Ventura et al. 1997;Notton 2007). Formally no species are known from the Oriental and Ethiopian regions, but Masner (1976) mentioned some undescribed species from both regions.
The subfamily Ismarinae has been studied mainly in the Holarctic and Neotropical regions, with no species known from China prior to this study. During recent years, we have accumulated many specimens of Diapriidae during our survey of the Hymenoptera of China. Among them, twenty five specimens belonging to the genus Ismarus represent five species, of which three species from the Oriental region of China are described as new to science in this paper and two species are newly reported from the Oriental and Palaearctic regions of China.

Materials and methods
Examined specimens were collected by sweeping and by yellow pan traps (YPT) from different provinces of China between 2006 and 2010. All specimens are deposited in the Hymenopteran Collection of South China Agricultural University, Guangzhou. For the examination, an Olympus stereomicroscope was used. The photographs are made by a digital camera (Q-Imaging, RTV) mounted on a Zeiss stereomicroscope and with Image-Pro Plus software.

Genus
Description. Body stout; body colour usually black, but brown in a few species. Head transverse in dorsal view, with sparse setae on face, frons and occiput; labrum exposed and sclerotized; mandible bidentate; palpal formula 4-3 or 5-3; antennae inserted low on face, close to clypeus; face with a distinct transverse carina below antennal sockets; antennal shelf not prominent; antenna of female 15-segmented, of male 14-segmented; modified male sex-segment is second flagellomere, rarely both first and second flagellomeres modified; eyes bare; occipital carina complete; pronotum dorsally and along anterior margin with long setae; mesoscutum convex, smooth; notauli reduced to anterior pits; humeral sulcus developed; anterior scutellar pit with a weak but distinct median longitudinal carina; scutellum posteriorly raised, with posterior margin truncate or round; metanotum crenulated, with median carina distinct; propodeum with distinct transverse and longitudinal carinae; metapleuron reticulate rugose, with dense setosity; fore wing with radial cell closed; fore tibia with regular spur and one false spur, hind tibia strongly incrassate; petiole short and transverse; base of second tergite with longitudinal furrows; sutures between tergites distinct or absent; sternite with fine setae. Biology. Some species of the genus are hyperparasitoids of Dryinidae (Hymenoptera). Ismarus flavicornis (Thomson, 1859) was reared from Anteon flavicorne (Dalman, 1818), I. halidayi was reared from an Anteon sp. and I. dorsiger was recorded to attack an Aphelopus sp. (Chambers 1955;1981;Nixon 1957;Jervis 1979).

Ismarus longus
Mesosoma. Mesosoma in dorsal view 0.8 times as long as width of head; pronotum angular in dorsal view, anteriorly rugose-punctate and setose; central part of lateral side of pronotum smooth, with anterior and upper margins rugose-punctate and setose; mesoscutum smooth and convex, with some sparse long setae near humeral sulcus and notauli; notauli anteriorly present, oblique long and pit-like, crenulate inside; humeral sulcus deep and crenulate, 1.4 times length of tegula; anterior scutellar pit crenulate, with weak median longitudinal carina; scutellum smooth, posterior rim rounded; propodeum rugose, with transverse and longitudinal carinae present; mesopleuron smooth and bare, with upper corner below tegula punctate and setose; metapleuron reticulate-rugose and setose.
Wings. Fore wing with costal, subcostal, basal, marginal, stigmal and postmarginal veins tubular; radial cell closed, 0.6 times length of marginal vein and 3.0 times as long as its height. Hind wing with a basal cell.
Legs. Fore and middle legs slender; hind tibia strongly incrassate.
Metasoma. Petiole transverse, weakly rugose and with longitudinal carinae; second tergite smooth and scattered with a few setae along lower side, median furrow extending to 0.4 length of second tergite; sutures between tergites complete and well impressed; sternites finely punctate and setose.  (1976) and is similar to Ismarus halidayi Foerster, 1850, but it differs from the latter by having the second flagellomere 5.0 times as long as wide (2.6 times as long as wide in I. halidayi), apical antennal segment 2.6 times as long as wide (2.0 times); notauli anteriorly present, oblique long and pit-like, crenulate inside (smooth) and the radial cell of fore wing shorter than marginal vein (radial cell as long as marginal vein).
Wings. Fore wing with costal, subcostal, basal, marginal, stigmal and postmarginal veins tubular; radial cell closed, 0.6 times length of marginal vein and 2.0 times as long as its height. Hind wing with a basal cell.
Legs. Fore and middle legs slender; hind tibia strongly incrassate. Metasoma. Petiole transverse, with irregular longitudinal carinae; second tergite smooth and with a few scattered setae along lower side, median furrow short, extending to 0.2 length of second tergite; seventh tergite densely punctate; sutures between tergites complete and well impressed; sternites finely punctate and setose.
Colour. Body black. Antenna entirely black. Legs brown, with coxae and trochanters black; fore and middle femora reddish brown with basal 0.3 and dorsal margin blackish; hind femur dark brown; hind tibia dark brown, with dorsal apical 3/4 brown. Wings hyaline, veins dark brown.

Distribution. China (Yunnan).
Material examined. Holotype, female. CHINA: Yunnan, Mt. Gaoligonshan (25. 98°N, 98.80°E), 2006.VII.20-21, Zhong-shi Zhou, No. 200700989. Diagnosis. This species belongs to the I. halidayi-group and is similar to Ismarus longus sp. n., but it can be easily distinguished from the latter by having the second flagellomere 3.5 times as long as wide (5.0 times in I. longus); the radial cell of the fore wing 2.0 times as long as high (3.0 times); the seventh tergite densely punctate (finely mat); and the antenna uniformly black, all trochanters black (scape, pedicel and first flagellomere dark brown, trochanters brown).
Etymology. The specific name refers to the black trochanters of this species. Holotype. Female. Body length 2.2 mm; fore wing length 1.8 mm.
Mesosoma. Mesosoma in dorsal view 0.75 times as long as width of head; pronotum angular in dorsal view, anteriorly punctate and setose; lateral side of pronotum with anterior and upper margins coarsely punctate, lower half rugose punctate, posterior upper part smooth; mesoscutum smooth and convex; notauli present as small pits on anterior face; humeral sulcus strong, 1.4 times length of tegula; anterior scutellar pit transverse, crenulate inside, median longitudinal carina weak; scutellum smooth, posterior rim weakly concave and subtruncate; propodeum rugose and punctate, with transverse carinae and longitudinal carinae strong; mesopleuron mostly smooth and bare, with upper corner below tegula finely punctate and setose; metapleuron rugose and setose.
Wings. Fore wing with costal, subcostal, basal, marginal, stigmal and postmarginal veins tubular; distal part of median and cubital veins weakly pigmented; radial cell closed, 0.3 times length of marginal vein and 2.3 times as long as its height. Hind wing with a basal cell.
Legs. Fore and middle legs slender; hind tibia strongly incrassate. Metasoma. Petiole transverse, rugose and with irregular longitudinal carinae; second tergite mostly smooth and scattered with a few setae along lower side, median furrow short, extending to 0.2 times length of second tergite; sutures between tergites complete and well impressed.
Colour Diagnosis. This species belongs to the I. halidayi-group and can be distinguished from I. halidayi by having the eye height 7.0 times length of the malar space (4.5 times in I. halidayi); the radial cell of the fore wing small and 0.3 times length of marginal vein (radial cell as long as marginal vein); the distal part of the median and cubital veins weakly pigmented (median and cubital veins distinctly pigmented); the posterior rim of the scutellum weakly concave and subtruncate (posterior rim of scutellum round).
Etymology. The specific name is derived from the Latin adjective 'parvi' (small) and 'cell', referring to the small radial cell of fore wing. (