Two new species of Centrodora (Hymenoptera, Aphelinidae) from China, with a key to Chinese species

Abstract Two new species of Centrodora Förster, C. crassiscapa sp. n. and C. pellucida sp. n., are described from China. A key to species from China based on females is given.


Introduction
Centrodora Förster, 1878 currently comprises 61 species (Noyes 2017). A majority of the species in this genus are oophagous, developing in the eggs of economically important Hemiptera and Orthoptera, whereas other species are known to attack nymphs of Hemiptera, and pupae of Diptera, Hymenoptera, and Coleoptera (Hayat 1974(Hayat , 2010Polaszek 1991). Several regional revisionary studies of the genus include Mercet (1918Mercet ( , 1930 and Nikol'skaya and Yasnosh (1966) on the European region, Hayat (1998Hayat ( , 2010 on the Indian region. The Chinese fauna of Centrodora is poorly known with only C. lineascapa Hayat known from the Fujian Province (Huang 1994), and C. idioceri Ferrière (Chou and Chou 1990) and C. locustarum (Giraud) (Chiu and Chou 1974) known from Taiwan. In the present paper, two new species are added to the Chinese fauna. A key to all five species from China based on females is given.

Materials and methods
All specimens in the present study were collected using yellow pan traps or Malaise traps, then dissected and mounted in Canada Balsam on slides following the method described by Noyes (1982). Photographs were taken with a digital CCD camera attached to an Olympus BX51 compound microscope and final modifications to the images were made using Adobe Photoshop. Most measurements were made from slidemounted specimens using a reticle micrometre except the total body length (excluding the ovipositor), which was measured from alcohol-preserved specimens before being dissected. All measurements are given in micrometres (μm) except body length, which is measured in millimetres (mm). Scale bars are 100 μm. All the specimens listed below are deposited in Northeast Forestry University, Harbin, China. Terminology follows Hymenoptera Anatomy Consortium (2017). Diagnosis. Centrodora crassiscapa sp. n. is easily distinguished by following combination of characters: enormously thick scape, largely dark brown mesosoma, completely dark brown metasoma, long and strongly exserted ovipositor.
Description. Female. Holotype. Length about 1.2 mm. Head dark brown. Eyes and ocelli dark brown. Antenna mostly brown, except pedicel and F1 paler. Mandible dark brown. Mesosoma largely dark brown, except metanotum and propodeum yellow. Median area of the mesoscutum and mesoscutellum with a distinctly pale midlongitudinal groove. Fore wing with basal one fourth hyaline, area posterior to marginal vein brown, remaining wing disc faintly infuscate; hind wing hyaline. Legs largely yellow, except fore leg with distal half of femur and tibia brownish-yellow; mesofemur and hind leg with coxa and femur brown. Metasoma dark brown to black.
Mesosoma. Pronotum imbricate, mesoscutum and mesoscutellum mainly polygonal reticulate. Mesoscutum with median area (Fig. 3) 0.83× as long as wide, 1.4× as long as mesoscutellum, and with 10 setae; each lateral area of the mesoscutum and axilla with 2 and 1 setae respectively; mesoscutellum (Fig. 4) 0.58× as long as wide, with 2 pairs of setae. Distance between anterior pair of scutellar setae 0.9× that between posterior pair. Placoid sensilla much closer to anterior pair of setae than to posterior pair. Fore wing 3.57× as long as wide, with marginal setae 0.08× wing width. Costal cell slightly longer than marginal vein, with 2 distal setae on dorsal surface; submarginal vein with 4 setae, marginal vein with 8 long setae along anterior margin, postmarginal vein short and about one third of length of stigmal vein; basal cell with 2 setae. Linea calva closed by a line of setae posteriorly. Hind wing (Fig. 6) 7.17× as long as wide, marginal setae about 0.53× as long as wing width. Mesotibial spur (Fig. 7)   Metasoma (Fig. 8) about 1.75× as long as mesosoma. Ovipositor 3.25× as long as mesotibia and strongly exerted, with the exerted part 0.46× as long as ovipositor. Third valvula 4.18× as long as mesobasitarsus. Length measurements: ovipositor, 1268; third valvula, 585.
Male. Length 0.73-0.78 mm. Colour similar to the female, except median area of mesoscutum a little paler.
Remarks. The new species is close to C. amoena Förster 1878, with similar colour on the head and metasoma and strongly exserted ovipositor. However, it can be separated from the latter by the thickened scape of the female antennae (normal in C. amoena), completely dark brown mesoscutum (vs largely yellow), clava 3.95× as long as wide (vs 3.5×), male antenna with F3 2.69-2.85× as long as wide (vs about 4×, cf. Nikol'skaya and Yasnosh 1966, fig. 162).
Host. Unknown. Etymology. Latin: crassus = thick, fat; and the specific name refers to the enormously thick scape of the female antennae.
Distribution. China (Heilongjiang).  Diagnosis. Centrodora pellucida sp. n. can be easily distinguished from other species in this genus by the following combination of characters: upper half of head yellowish-brown; gaster dark brown; fore wing mostly infuscate and paler distally, with a wide transparent cross band on the median area of disc as in Fig. 16; F2 subquadrate, and ovipositor strongly exserted.
Description. Female. Holotype [The colour of body faded during slide mounting, and the following descriptions of colour is based on alcohol-preserved specimens]. Length 0.95 mm. Head with frontovertex, upper face, and occiput above foramen yellowish brown; remainder of head brown. Eyes and ocelli yellowish-brown. Antenna brown. Mandible yellowish-brown, with apex dark brown. Mesosoma largely yellowish-brown, but with mesopleuron brown and with a pale yellow mid-longitudinal groove on median area of mesoscutum, mesoscutellum, metanotum, and propodeum. Fore wing mostly infuscate and paler distally, with a wide transparent cross band on the median area of disc as in Fig. 16. Hind wing faintly infuscate. Leg mostly brownish; mesocoxa paler; meso-and metafemur, both basal one third of meso-and metatibia dark brown. Metasoma mostly dark brown, with petiole and third valvula yellowish.
Mesosoma with fine, elongate reticulations on median area of mesoscutum and mesoscutellum (Figs 14, 15). Median area of mesoscutum 0.93× as long as wide, 1.53× as long as mesoscutellum, and with 10 setae; each lateral area of the mesoscutum and axilla with 2 and 1 setae respectively; mesoscutellum 0.73× as long as wide, with 2 pairs of setae. Distance between anterior scutellar setae subequal to that between posterior pair. Placoid sensilla much closer to anterior pair of setae than to posterior pair. Fore wing (Fig. 16) 4.21× as long as wide, marginal setae 0.22× wing width. Costal cell slightly shorter than marginal vein, with 1 distal seta on dorsal surface; submarginal vein with 4 setae, marginal vein with 6 long setae along anterior margin, postmarginal vein 0.5× as long as stigmal vein; basal cell without seta. Linea calva closed by a line of setae posteriorly. Hind wing (Fig. 17)  Metasoma (Fig. 19) about 1.4× as long as mesosoma. Ovipositor 2.45× as long as mesotibia and strongly exserted, with the exserted part 0.35× as long as ovipositor. Third valvula 3.07× as long as mid basitarsus. Length measurements: ovipositor, 613; third valvula, 230.

Remarks.
The new species is very close to C. amoena Förster 1878 in having similar colour of the body and strongly exserted ovipositor. But it can be separated from the latter by F1 with ventral margin very slightly shorter than F2 (vs obviously shorter, cf. Nikol'skaya and Yasnosh 1966, fig. 150), F2 subquadrate (vs about 1.8× as long as wide), clava 4.0× as long as wide (vs 3.5×), fore wing mostly infuscate, with a transparent cross band on the median area of disc (vs mostly hyaline with the area beneath marginal vein and stigmal vein infuscate).
Host. Unknown. Etymology. The specific name refers to the fore wing with a wide transparent cross band on the median area of disc.