Revision of Streblocera Westwood (Hymenoptera, Braconidae, Euphorinae) from China, with the description of seven new species

Abstract The Chinese fauna of the euphorine genus Streblocera Westwood, 1833 (Hymenoptera, Braconidae) is revised. Seven new species from China are described and illustrated: Streblocera (Eutanycerus) carinifera Li, Chen and van Achterberg, sp. nov., S. (E.) laterostriata Li, Chen and van Achterberg, sp. nov., S. (E.) uncifera Li, Chen and van Achterberg, sp. nov., S. (S.) interrupta Li, Chen and van Achterberg, sp. nov., S. (S.) stigenbergae Li, Chen and van Achterberg, sp. nov., S. (S.) trullifera Li, Chen and van Achterberg, sp. nov., and S. (S.) zoroi Li, Chen and van Achterberg, sp. nov. An identification key to the females of Streblocera from China is provided.


Introduction
Euphorinae (Hymenoptera, Braconidae) is a large subfamily of endoparasitoid wasps with more than 1,270 described species worldwide (Yu et al. 2016). In addition to the Aphidiinae, they are the only known Braconidae wasps attacking adult hosts. The most commonly used hosts are adult Coleoptera, especially of the families Chrysomelidae and Curculionidae, but adult Hymenoptera, Neuroptera, Hemiptera, Psocoptera and, rarely, Orthoptera are used (Shaw 1985;Stigenberg et al. 2015). Obviously, coping with adult insect hosts was the major cause of the high diversity observed in adult Euphorinae.
Their special morphological structures are apparently modified for grasping more aggressive adult hosts during oviposition. One of the most bizarre modifications found in the Braconidae is in the females of Streblocera; here the antennae became raptorial. Typically, the scape has a unique horn, and one or more flagellomere are flattened and provided with claw-like structures. In many of the tropical species, the raptorial condition of the female antenna is accentuated by an unusual long scape (Shaw 1985).
The antennae of female euphorine genera Betelgeuse, Marshiella, Streblocera, and Ropalophorus are uniquely modified, and they are all koinobiont endoparasitoids of adult Coleoptera (but the host of Betelgeuse is yet unknown). In the most recent phylogeny by Stigenberg et al. (2015) Streblocera is included in the tribe Townesilitini, together with Marshiella, Townesilitus, and Proclithrophorus, while Betelgeuse is included in the Dinocampini and Ropalophorus in the Cosmophorini. Chen and van Achterberg (1997) divided the genus Streblocera into five subgenera: Asiastreblocera, Cosmophoridia, Eutanycerus, Villocera, and Streblocera. However, specimens sometimes combine characteristics of different subgenera, especially of Eutanycerus and Villocera and both were synonymized by Belokobylskij (2000). Therefore, we consider the use of subgenera provisional without large-scale DNA-sequencing efforts and, for the moment, we use them for convenience.
Currently, 121 valid species of the genus Streblocera are known. To date, the subgenus Asiastreblocera comprises five species from the Oriental region and three species from the Palaearctic region; the subgenus Cosmophoridia comprises one species from the Oriental region and one species from the Palaearctic region; the subgenus Eutanycerus comprises 47 species from the Oriental region and ten species from the Palaearctic region; the subgenus Villocera comprises one species from the Oriental region and one species from the Palaearctic region; finally, the subgenus Streblocera comprises 18 species from the Oriental region and 12 species from the Palaearctic region (Yu et al. 2016;Long and Nhi 2020). From the Neotropical region only one described species is known, which belongs to the subgenus Lecythodella. It is characterised by having the malar suture deep and clearly defined, the dorsal carinae of first metasomal tergite absent, the third antennal segment shorter than the fourth segment and the occipital carina absent medio-dorsally. Stigenberg and Zhang (2020) included two species from New Guinea in Streblocera lacking the enlarged scapus (the scapus is much shorter than the third antennal segment) and having no dorsope in the first metasomal tergite. The enlarged scapus (longer than the first flagellomere and at least reaching upper level of vertex in lateral view, if intermediate then should have dorsope present) is generally used in the recognition of the genus, e.g. Shaw (1985), Chen and van Achterberg (1997), and Long and Pham (2020). Only the distinctly raised antennal sockets and molecular data hint to a relationship with Streblocera and, therefore, the inclusion of both species in Streblocera is questionable and likely both species belong to a new genus of the Streblocera clade.

Materials and methods
Studied material was selected from the entomological collections of Biological Control Research Institute, Fujian Agriculture and Forestry University, Fuzhou, China (FAFU) (former Beneficial Insects Institute, China (BIIC)). The specimens were collected using a sweep net. All specimens studied are deposited in FAFU.
The specimens were examined using a Zeiss Stemi 2000 stereomicroscope. Photographs were taken with a Leica DFC450 digital camera mounted on a Leica M205C stereo microscope. All images were further processed using minor adjustment in Adobe Photoshop CC. Morphological terminology follows van Achterberg (1988van Achterberg ( , 1993, including the abbreviations for the wing venation. Sclerite surface sculpturing follows Eady (1968). Measurements are taken as indicated by van Achterberg (1988). For identification of the subfamilies, see van Achterberg (1993), for a key to the genus see Shaw (1985).
Biology. Unknown. Distribution. Oriental: China (Fujian). Etymology. Named after the ventral carina of the first to fifth flagellomeres: carina means keel in Latin and fero is Latin for to carry. Figure 4A-B Streblocera chaoi You and Zhou, 1993: Figure 5A Description. Holotype, ♀, length of antenna 3.9 mm, of fore wing 3.3 mm, and of body 4.0 mm (Fig. 7A).
Colour. Dark brown to black; face, basal part of antenna and of ovipositor sheath and ovipositor dark brown; wing membrane infuscate, pterostigma and veins dark brown.
Remarks. This new species can be distinguished from related species by its unique "simple" antenna. Only S. (E.) sichuanensis Wang, 1986 shares this character with new species, but the new species differs from it as follows: (i) antenna with 24 antennomeres, scapus 7.5× longer than its maximum width (antenna with 21 antennomeres, scapus 5.7× longer than maximum width in S. sichuanensis); (ii) first metasomal tergite 2.0× longer than its apical width, striate laterally (first tergite 2.5× longer than its apical width, smooth laterally); (iii) propodeum without basal carina (propodeum with basal carina); (iv) ovipositor long and straight (ovipositor curved apically).
Biology. Unknown. Distribution. Oriental: China (Yunnan). Etymology. Named after the laterally striate first tergite; "lateralis" is Latin for "of the side" and "stria" is Latin for "line".
Remarks. This new species is similar to S. (E.) hsiufui You, 1999, but differs from it as follows: (i) first to seventh flagellomeres serrate ventrally, only the carina of seventh flagellomere with hook (first to seventh flagellomeres serrate ventrally and all with hook in S. hsiufui); (ii) first metasomal segment more robust, 1.7× longer than its apical width (first metasomal segment 2.3× longer than its apical width); (iii) ovipositor sheath more robust and ovipositor curved upwards (ovipositor sheath slender and ovipositor wave-like bent); (iv) body yellowish brown to brown (body dark brown).
Colour. Yellowish brown to dark brown; palpi, basal antenna and legs yellowish brown; antenna and head largely brown; wing membrane hyaline, pterostigma and veins brown.
Remarks. This new species is similar to S. (S.) latiscapus Belokobylskij, 2000, but differs from it as follows: (i) antenna with 15 antennomeres, first flagellomere 5.8× longer than second flagellomere (antenna with 17-18 antennomeres, first flagellomere 2.8-3.0× longer than second flagellomere in S. latiscapus); (ii) eye 1.8× longer than temple in dorsal view, inner side of eye curved (eye 1.6× longer than temple in dorsal view and inner side of eye straight).
Colour. Yellowish brown to dark brown; face, basal part of antenna, palpi and legs yellowish brown; scutellum, metanotum, brown; wing membrane hyaline, pterostigma and veins dark brown; second to thirteenth flagellomeres, propodeum and metasomal segments dark brown.
Remarks. This new species can be distinguished from related species by the combination of 15 antennomeres, scapus without horn, first and second flagellomere densely setose and modified, occipital carina narrowly interrupted medio-dorsally, very wide scutellar sulcus and ovipositor short and strongly curved upwards.
Biology Remarks. The studied specimens differ as follows: scapus fairly long and weakly expanded, 5.0× longer than its maximum width (scapus more robust, expanded, 4.4-4.5× longer than its maximum width according to the original description). Description. Holotype, ♀, length of antenna 1.5 mm, of fore wing longer than 2.2 mm, and of body 2.5 mm.
Colour. Yellowish brown to dark brown; palpi pale yellow; basal part of antenna, head and legs yellowish brown; antenna and mesopleuron largely brown; wing membrane hyaline, pterostigma and veins brown.
Remarks. This new species can be distinguished from related species by its combination of 17 antennomeres, scapus with a spoon-shaped horn basally and vein SR1+3-SR of fore wing largely unsclerotized.
Biology. Unknown. Distribution. Palaearctic: China (Liaoning). Etymology. Named after its spoon-shaped horn of the scapus: "trulla" is "little spoon" in Latin and "fero" is Latin for "carry". Description. Holotype, ♀, length of antenna 2.2 mm, of fore wing longer than 2.6 mm, and of body 2.6 mm.
Colour. Yellowish brown to dark brown; palpi pale and legs yellowish brown; head, ovipositor sheath and ovipositor brown; antenna brown, but its basal two segments yellowish brown; wing membrane slightly infuscate, pterostigma and veins brown; body dorsally dark brown.
Remarks. This new species is distinguished from related species by its combination of 18 antennomeres, scapus with two specialized horns, first and second flagellomere modified and occipital carina narrowly interrupted medio-dorsally.
Biology. Unknown. Distribution. Palaearctic: China (Hubei). Etymology. The species is named after the virtual character Roronoa Zoro, who is a great swordsman in the Japanese animation "One Piece". The scapus and the first flagellomere of the new species form three catch structures similar to the three swords of Zoro.