Plagiotrochus hepingensis Wang, Wang & Zhu, 2021

Wang, Qing, Wang, Xiu-Dan & Zhu, Dao-Hong, 2021, A new species of Plagiotrochus from China (Hymenoptera: Cynipidae: Cynipini) galling on Quercus glauce (Fagaceae), Zootaxa 4995 (2), pp. 389-395 : 390-394

Plagiotrochus hepingensis Wang, Wang & Zhu , sp. n.

( Figures 1-13 )

urn:lsid:zoobank.org:pub:408D6536-72F9-4A3C-925D-30F7F9C5383A

Type material. Holotype: female, CHINA, Hunan Province, Changsha County, 2018. III.10-20, leg. Yin Pang ; Paratypes: 2 females, same data as holotype. The holotype was dissected for photography, and the resultant body sections were dried and mounted on card points. One of the paratypes is incomplete because the metasoma was used for DNA extraction. All type specimens are deposited in the Insect Collection , Central South University of Forestry and Technology ( CSUFT), Changsha , Hunan, China .

Diagnosis. The new species is similar to the sexual female of Plagiotrochus masudai Ide, Wachi et Abe, 2010 , but can be easily distinguished from the latter by the following features. Firstly, the galls of P. masudai occur in buds ( Ide et al. 2010: Figs. 26-27), while the galls of P. hepingensis sp. n. are attached along the midrib on the abaxial surface of the leaf blade. Secondly, the mesosoma has notauli obscured by surface sculpture in P. masudai ( Ide et al. 2010: Fig. 11 ), whereas mesosoma is less rugose with distinct notauli in the new species. Thirdly, the median propodeal area lacks a median propodeal carina in P. masudai ( Ide et al. 2010: Fig. 12 ), whereas P. hepingensis sp. n. has a complete median propodeal carina.

Description. Female.

Length. 2.3–2.5mm (N = 2).

Coloration. Head dark brown to black with lower face and clypeus reddish-brown. Eyes charcoal grey and ocelli pale grey. Antenna pale, uniformly yellowish-brown. Mandibles reddish-brown with black tooth, maxillary and labial palps brown. Front legs with basal half of coxa, tibia, tarsomeres 1 and 5 yellow, and tarsal claw of front leg dark, and end of coxa, femur and tarsomeres 2–4 yellow; the remaining legs uniformly yellowish-brown, except for dark tarsomere 5 and tarsal claw. Mesosoma black. Metasoma mostly dark brown and graduating to light brown posteriorly; ventral spine of hypopygium light yellowish-brown. Wings with all visible veins yellowish-brown.

Head ( Figs. 3-6 ). 1.25 times as wide as high, broader than mesosoma in anterior view. Gena slightly broadened behind compound eye in anterior view and longer than eye width in lateral view. Compound eyes converging ventrally; height of compound eye longer than length of malar space. Frons reticulate rugose; lower face laterally with very clearly radiating striae from clypeus to lower level of eyes. Malar space alutaceous, a little more than 0.3 times eye height. Lower face, malar space and clypeus with sparse setae. Clypeus trapezoid-shaped. Anterior tentorial pits large, rounded; epistomal sulcus and clypeo-pleurostomal line distinct, but anterior tentorial pits indistinct. Transfacial distance 1.3 times compound eye height; toruli located equidistant from vertex and clypeal margin, distance between inner margin of eye and outer rim of antennal torulus 2.32 times distance between antennal toruli and 1.41 times diameter of torulus. Posterior ocelli rounded, narrowly separated from each other, ratios of POL/OOL, POL/LOL, and LOL/OOL are 0.81, 2.2 and 0.4, respectively; LOL 3.0 times the diameter of ocellus; in dorsal view, posterior margin of anterior ocellus almost aligned with anterior margin of posterior ocelli. Vertex and interocellar area coriarious to finely reticulate with some rugae. Postgena with radiating striations and scattered setae; occiput mostly polished with scattered setae. Area around occipital foramen impressed and glabrous. Gular sulcus and posterior tentorial pits distinct.

Antenna ( Fig. 2 ). Antenna filiform with 12 flagellomeres; pedicel 1.59 times as long as broad; relative lengths of scape, pedicel and F1–F12: 15:12:17:15:16:16:15:14:13:13:12:11:11:20; placoid sensillae distinctly visible on F2–F12, absent in F1.

Mesosoma ( Figs. 7-9 ). Slightly longer than higher in lateral view (1.36 times). Pronotal median length three fifths of length of outer lateral margin. Anterior plate of pronotum glabrate medially with few short setae laterally. Mesoscutum very slightly longer than wide (1.03 times), measured at anterior tip of tegulae, surface mostly alutaceous, distinctly striate-rugose in posterior half between notauli; notauli complete, anteriorly and posteriorly obscured by surface grooves, along with few white setae; base of notaular grove with transverse carinae; anterior parallel lines absent, their position only indicated by two smooth and shiny marks. Mesoscutellum broader than long (1.95 times), rounded posteriorly. Scutellar foveae deeply impressed and glabrous, separated medially by a broad coriaceous carina. Mesopleuron punctated with scattered setae in the ventral-posterior corner area. Mesopleural triangle rugulose. Metapleural sulcus reaching mesopleuron in upper two-thirds of its height. Metascutellum glabrous and coriaceous, as long as ventral impressed area. Metanotal trough smooth, glabrous, without setae. Lateral propodeal carinae distinct, strongly curved outward in middle section; medial propodeal area with a complete median propodeal carina and a few incomplete longitudinal wrinkles; lateral propodeal areas with dense white setae.

Legs. Tarsal claws with basal lobe bent; base expanded to a small pronounced lobe ( Fig. 13 ).

Wing ( Fig. 12 ). Wing with distinct veins R+Sc, R1+Sc, Rs, M，Rs+M, M, M+Cul, Cu-a, Cul, Culb, Cula, 2r and R1; Forewing longer than body, hyaline, with dense cilia on margin, veins light brown, radial cell open, 4.5 times as long as broad; Rs and R1 not reaching wing margin; areolet distinct and large; radial cell 4.5 times as long as wide. Rs+M distinct, its projection reaching basalis below half of its height.

Metasoma ( Figs. 10-11 ). Longer than head+mesosoma, slightly longer than height in lateral view; abdominal tergite II 2.1 times as high as long in lateral view, smooth, extending to 2/3 length of metasoma in dorsal view, with numerous white setae anterolaterally; tergite III-VI finely punctate; tergite VII and VIII posteriorly with long setae. Prominent part of ventral spine of hypopygium short, tapering gradually; subapical setae long and reaching beyond the apex of the spine.

Male unknown.

Biology. All specimens were reared from galls collected from Q. glauca Thunberg in early March. The attacked leaves seem healthy and undamaged on dorsal surface. The galls were situated on the midrib of the abaxial surface of young leaves, either scattered or concentrated along the midrib. Each gall shape was gemmiform, suberin, 1-1.9 mm in height, unilocular, yellowish brown ( Fig. 14). Sexual adults emerged in mid-March.

Distribution. Known from Changsha City, Hunan Province, China.

Host Plant. Quercus glauca Thunberg.

Etymology. The species epithet is named after the locality of the holotype, Heping Village. Noun in the genitive case.

Comments. The new species, Plagiotrochus hepingensis sp. n. described herein was reared from galls formed on the central vein on the abaxial surface of leaf blade of Quercus glauca Thunberg ( Figs. 13 ). Compared to other species of genus Plagiotrochus , especially to the most morphologically similar species, Plagiotrochus masudai Ide, Wachi et Abe , which also shares the same host plant, we established that the new species is unique based on the combination of the following characters: gall location; gall structure; structure of the notauli; and presence of a median propodeal carina.

A total length of 678 bp COI gene sequences were generated from Plagiotrochus hepingensis sp. n. and Plagiotrochus masudai Ide, Wachi et Abe , with the Genbank accessions MW792414 and MW800327 respectively. The pairwise distance between those two species is 3.8%, which supports the recognition of these two species as distinct. The biology of the new species is mostly unknown except that adults of the species emerged in mid-March. We hypothesis that the specimens examined here represent the sexual form of the new species, even though only three females were successfully reared from the collected galls, and the male and asexual form of the new species is still unknown.

Figures

FIGURES 1-6. Plagiotrochus hepingensis sp. n., holotype female. 1. General habitus 2. Antenna 3. Head, front view 4. Head, posterior view 5. Head, dorsal view 6. Head, lateral view.

FIGURES 7-13. Plagiotrochus hepingensis sp. n., holotype female. 7. Mesosoma, lateral view 8. Mesosoma, posterior view 9. Mesosoma, dorsal view 10. Metasoma, lateral view 11. Metasoma, posterior view 12. Fore wing 13. Hind tarsal claw.