A new species of Bicurta Sheng et al. from China (Hymenoptera, Ichneumonidae, Collyriinae), a parasitoid of Stenocephus fraxini Wei (Hymenoptera, Cephidae)

A new species of the genusBicurtaSheng, Broad & Sun, 2012, is described and illustrated,B. hejunhuaisp. nov., from North and Northeast China. The new species was reared from the stem-sawflyStenocephus fraxiniWei (Hymenoptera, Cephidae), which is the first host record for the genusBicurta.

The genus Bicurta is monotypic, with only the type species B. sinica described from Jiangxi Province of China (Sheng et al. 2012). Shang et al. (2016) reported a male specimen of B. sinica from Liaoning Province in Northeast China. The biology of the genus Bicurta was not known until this study.
The aim of this study is to describe a new species of Bicurta parasitizing S. fraxini Wei.

Materials and methods
Parasitoids were reared in the laboratory from larvae of Stenocephus fraxini collected in branches of Fraxinus spp. from North and Northeast China (Inner Mongolia, Liaoning and Heilongjiang), mainly from the downtown of Shenyang City. Photographs were taken using a KEYENCE VHX-5000 Digital Microscope imaging system and processed with Photoshop CS software. Morphological terms follow Broad et al. (2018). Abbreviations used in the text are as follows: POL = the shortest distance between posterior ocelli; OD = diameter of a posterior ocellus; OOL = the shortest distance between a posterior ocellus and a compound eye. Type material of the new species is deposited in South China Agricultural University, Guangzhou, Guangdong (SCAU).

Genus Bicurta Sheng, Broad & Sun, 2012
Type species. Bicurta sinica Sheng et al., 2012. Diagnosis. This genus is distinguished from Collyria by the epicnemial carina indistinct because of sculpture on the mesopleuron; ovipositor straight and smooth (Fig. 12), lacking teeth on the ventral valve; and the fore and mid tarsal claws each having an acutely lobed tooth (Figs 10, 24) (Sheng et al. 2012), while in the other two other collyriine genera, Aubertiella and Collyria, fore and mid tarsal claws with a median tooth, rather than a lobe.
Biology. Adults of the new species emerged from larvae of Stenocephus fraxini Wei (Hymenoptera, Cephidae) from March to May 2019 in Northern China. This is the first report of a host of Bicurta, which is consistent with the known biology of Collyria, as parasitoids of stem-sawflies (Hymenoptera, Cephidae).
Based on the field work survey during 2018 to 2019, the parasitism rate of this species on S. fraxini was 59.3% on average in the downtown of Shenyang city (J.H. Yan, unpublished data Description. Holotype, female ( Fig. 1). Body length 10.0 mm, fore wing length 6.2 mm, antenna length 3.8 mm, ovipositor length 1.6 mm.
Head. Face flat (Fig. 2), 1.2× as wide as high, centrally with sparse punctures, distance between punctures of central area 1.0 to 5.0× diameter of punctures, punctures close below antennal sockets and near inner orbits; face next to inner orbit with fine granular texture. Clypeus ( Fig. 1) 2.2× as wide as high, finely and sparsely punctate, apical margin with an obtuse median tubercle, impunctate. Mandible weakly narrowed to apex, middle width of mandible 0.57× as wide as basal width of mandible, with lower tooth slightly longer than upper tooth. Labrum not exposed. Malar space short ( Fig.  4), finely wrinkled and with fine leathery texture in between, 0.33× as long as basal mandibular width. Gena (Fig. 3) evenly convergent posteriorly, finely punctulate and pubescent, 0.63× as long as eye in dorsal view. Vertex ( Fig. 3) with posterior portion finely punctulate, between lateral ocellus and eye with fine leathery texture. POL = 1.0, OD = 1.25, OOL = 1.0. Interocellar area flat with a short longitudinal groove. Frons finely punctate above antennal sockets, centrally with a weak longitudinal carina extending between antennal sockets to median ocellus, frons slightly rugose along carina sides. Antenna (Fig. 8) with 19 flagellomeres, ratio of length of basal five flagellomeres as follows: 1.42 : 1.25 : 1.17 : 1.08 : 1.0, first flagellomere 2.83× as long as its apical width, apical flagellomere 2.4× as long as its basal width, slightly shorter than fourth flagellomere (12 : 14). Occipital carina sharp and strong. Distance from hypostomal carina to mandible 1.25× longer than basal mandibular width.
Colour. Body mainly black. Head black, face with a pair of obscure yellow marks laterally just above tentorial pits; these yellow marks are very distinct in female paratypes (Fig. 20) and hardly discernible in holotype (Fig. 2). Mandible testaceous with   lower margin and apical teeth black. Stipes and prementum black. Labial and maxillary palpi yellow. Antenna with scape and pedicel black, flagellum dorsally blackish brown and ventrally yellowish brown. Fore and mid legs buff with coxae black; hind leg black, apex of trochanter yellow, trochantellus blackish brown, proximal base of hind femur ventrally buff, proximal half of hind tibia ventrally dull yellow and dorsally dark brown to blackish brown, apical half of hind tibia black. Hind margins of tergites 1-7 narrowly yellow. Tegula black. Wings hyaline, with veins and pterostigma blackish brown.
Male (Fig. 18, 19, 21, 22). Body length 8.2 mm, fore wing 5.4 mm. similar to female. Differences from female as follows: antenna ventrally yellow to yellowish brown; face and clypeus (except lower margin blackish) yellow (Fig. 19), sometimes with a small blackish spot on face centrally; frons with several transverse wrinkles just above antennal sockets; first tergite centrally with two distinct carinae which extend to posterior 0.7 of tergite, posterior tips of carinae irregularly branched. Paramere apically truncate.
Etymology. The new specie is named in honour of Prof. He Junhua from Zhejiang University in recognition of his years of dedicated and conscientious performance in the study of Chinese Hymenoptera, and also for the celebration of his 90 th birthday.
Comparison. The new species is similar to the genotype, B. sinica, in its overall appearance and colour pattern. But it can be distinguished from B. sinica by the face having two obscure or distinct yellow marks (the face of B. sinica has the ventral inner orbits, clypeus and a stripe passing through the anterior tentorial pits yellow); the mandible weakly narrowed from middle toward the apex, with middle width of mandible 0.57× as wide as the basal width of mandible (B. sinica with the mandible strongly narrowed from middle toward the apex, with middle width of mandible 0.26× as wide as the basal width of mandible, measurements based on the figure of Sheng et al. (2012); the central part of the face with sparse punctures (with dense punctures in B. sinica); the mesosternum polished, with sparse punctures (B. sinica has the mesosternum densely punctate); and the fore wing vein 1cu-a usually distinctly distad of M&RS (1cu-a opposite M&RS in B. sinica).
Biology. The species was reared from the larvae of Stenocephus fraxini Wei (Hymenoptera, Cephidae) in Northern China.

Discussion
Knowledge of the biology of the subfamily Collyriinae has been limited to life history studies of just two species of Collyria (Salt, 1931;Wahl et al. 2007). Both Collyria coxator (Villers) and C. catoptron Wahl have been shown to be koinobiont endoparasitoids of Cephus (Hymenoptera: Cephidae), ovipositing in the host egg and emerging from the cocooned larva. Sheng et al. (2012) presented detailed morphological evidence that placed the genus Bicurta in the subfamily Collyriinae, despite the very different morphology of the ovipositor. Confirmation that B. hejenhuai sp. nov. is also a parasitoid of larval Cephidae, but in a different habitat (tree twigs as opposed to grass stems) suggests that all collyriines may be koinobiont endoparasitoids of larval cephid sawflies, including the poorly known Aubertiella nigricator (Aubert), which has never been reared. The fine ovipositor of Bicurta species suggests that oviposition will be into host eggs or early instar larvae, although this has not been confirmed.