A new genus and species of Ctenopelmatinae (Hymenoptera, Ichneumonidae) from China

A new genus, Unicarinata Sheng, Li & Sun, gen. nov. , of the ichneumonid subfamily Ctenopelmatinae, is described for one new species, Unicarinata ventrialis Sheng, Li & Sun, sp. nov. The new genus is similar to Syntactus Förster, 1869 or Pion Schiødte, 1839, and different in having the propodeum with only one median transverse carina, areas and lateromedian longitudinal carinae entirely absent, tergite 1 straight, tergite 2 shagreened, impunctate, ovipositor straight. Types were collected from Mts Emei, Laojun, and Wawu in the Giant Panda National Park, Sichuan Province, Mts Fanjing and Leigong, Guizhou Province, and Mt Dayao, Guangxi Zhuang Autonomous Region, China.


Introduction
The Ctenopelmatinae are a large subfamily of ichneumonid wasps currently comprising 110 genera and 1617 described species, most of which are koinobiont endoparasitoids of sawflies of the superfamilies Pamphilioidea and Tenthredinoidea (Aubert 2000;Yu et al. 2016;Khalaim et al. 2019;Kasparyan 2020aKasparyan , b, 2021Sheng et al. 2020Sheng et al. , 2022Sun et al. 2021a, b;Watanabe 2021;Li and Sun 2022). The subfamily is subdivided into nine tribes, eight of which have been reported in China (Townes 1970;Yu et al. 2016;Sheng et al. 2020).
In the last three years the authors have been studying the ichneumonids of Mts Emei, Guanwu, Jiuzhaigou, Laojun, Qionglai, and Wawu (Giant Panda National Park), Sichuan Province, situated along the upper reaches of the Yangtze River, which belongs to the southern border of the Palaearctic part of China; Mts Fanjing and Leigong, Guizhou Province, and Mt Dayao, Guangxi Zhuang Autonomous Region, which belongs to the northern border of the Oriental part of China.
One species is a distinctive pionine, but proved very difficult to place in any genus, with a combination of character states that could almost feasibly place it in Syntactus Förster, 1869 or Pion Schiødte, 1839. For example, both genera have the outer face of the mandible without a basal transverse impression, lower tooth of mandible longer than upper tooth, upper end of epicnemial carina reaching the front edge of the mesopleuron, glymma absent, areolet absent. But propodeum of the new species (Fig. 8) has only one distinct median transverse carina, lack areas, the lateromedian longitudinal carinae are entirely absent, tergite 1 (Figs 13, 14) is very long and slender, straight, tergite 2 ( Fig. 15) is shagreened, impunctate, and the ovipositor is straight. We hypothesized that this species represents a new genus.

Materials and methods
Specimens of the new species were collected by interception traps (IT) (Li et al. 2012)  Images were taken using a Leica M205A stereo microscope with LAS Montage MultiFocus. The final images were edited in Adobe Photoshop CC. Morphological terminology follows Gauld (1991) and Broad et al. (2018).

Taxonomy
Etymology. The name of the new genus is derived from the propodeum having one strong transverse carina. The gender is feminine.
Remarks. The new genus is similar to Syntactus Förster, 1869 in having the apical margin of the clypeus blunt; base of the mandible without a transverse impression; dorsal end of epicnemial carina almost reaching the front edge of the mesopleuron; glymma absent; areolet absent; however, it can easily be distinguished from Syntactus by the following characters in combination: apical margin of clypeus medially almost truncate (Fig. 3); propodeum with only one strong transverse carina (Fig. 8); area superomedia entirely absent; hind vein 1-cu opposite cu-a; vein 2-cu absent; tergite 1 (Figs 12-14) very slender, straight; tergite 2 ( Fig. 15) granulate; and ovipositor ( Fig. 12) straight. In Syntactus the apical margin of the clypeus is almost evenly arcuate; propodeum is completely areolated, area superomedia at least partly present; tergite 1 relatively slender, decurved; tergite 2 smooth; and ovipositor upcurved.
Distribution. China (Guangxi, Guizhou, Sichuan). Etymology. The specific name is derived from the short and evenly convex mesosternum.