Plagiotrochus glaucus Melika & Tang

Tang, Chang-Ti, Melika, George, Yang, Man-Miao, Nicholls, James A. & Stone, Graham N., 2011, New species of oak gallwasps from Taiwan (Hymenoptera: Cynipidae: Cynipini), Zootaxa 2865, pp. 37-52 : 46-52

Plagiotrochus glaucus Melika & Tang , new species

Figs 39–56

Type material. HOLOTYPE female: TAIWAN, Nantou County, Lienhuachih Forest Research Centre, ex Quercus glauca , 23.X.2008. leg. J. Nicholls. Thirty-four female PARATYPES with the same labels as the holotype. The female holotype and 5 paratypes are deposited in NMNS, 15 female paratypes in PDL, 4 female paratypes in USNM, 4 female paratypes in AMNH, 5 female paratypes in NCHU.

Etymology. The species is named after the host plant, Quercus glauca Thunb. on which it induces galls.

Diagnosis. There are no Plagiotrochus species known from the Far East of Russia, Japan and China, thus no obvious species to compare with P. glaucus . More details are presented in Comments below. But the species does possess the diagnostic characters of Plagiotrochus : malar sulcus absent, lower face with few striae radiating from clypeus; mesoscutum transversely rugose, 1.3-2.0 times longer than broad; central propodeal area broad, delimited by strongly outwards curved lateral propodeal carinae; median longitudinal carina present; forewing margin always with long cilia.

Description. ASEXUAL FEMALE. Entire body uniformly chestnut reddish brown, with slightly lighter genae, antennae and legs; metasoma slightly darker dorsally and laterally.

Head massive, rounded in anterior view, dull, rugose, with some white setae, more dense setation in lower face; 1.9–2.0 times broader than long from above, 1.2 times broader than high and slightly broader than mesosoma in anterior view. Gena uniformly and delicately coriaceous to reticulate, broadened behind eye, nearly as broad as cross diameter of eye; malar area coriaceous, with some striae extending to eye margin, 0.4 times height of eye. Inner margins of compound eyes slightly converging ventrally. POL 0.8 times OOL; OOL 3.6 times longer than lateral ocellus and 2.7 times LOL; all ocelli elongated, ovate, of same size and shape. Transfacial distance 1.2 times height of eye; diameter of antennal toruli 2.2 times larger than distance between them, distance between torulus and inner margin of eye 1.2 times diameter of torulus; lower face coriaceous, with dense white setation; rugae irradiating from clypeus extending into area between eye and torulus; median elevated area of lower face coriaceous. Clypeus rounded, nearly as broad as high, emarginate, without median incision ventrally, alutaceous to glabrous, with small elevated rugose central area; anterior tentorial pit distinct, large, epistomal sulcus and clypeo-pleurostomal line distinct, deep. Frons rugose, shiny, with small smooth, shiny impression below median ocellus, with some white setae; interocellar area with strong rugae. Vertex and occiput uniformly coriaceous. Postocciput and postgena reticulate, shiny, impressed around occipital foramen, with some setae; posterior tentorial pit large, ovate, deep; height of occipital foramen nearly equal to height of coriaceous postgenal bridge; hypostomal carina emarginate, continuing into postgenal sulcus, not united medially. Antenna with 12 flagellomeres, slightly longer than mesosoma; pedicel longer than broad; F1 1.2 times longer than F2, 1.7 times longer than pedicel and nearly equal to length of scape; F2–F4 progressively shorter; F5–F11 nearly equal in length; F12 1.7 times longer than F11; placodeal sensilla present on F3–F12, absent on F1–F2.

Mesosoma elongate, 1.3 times longer than high. Pronotum dull, rugose, with some white setae, rugae with anastomoses, area between rugae smooth, shiny; propleuron brown, delicately coriaceous to alutaceous, shiny, concave in medio-central part. Mesoscutum uniformly dull, rugose, with rugae orientated mainly transversely, with numerous anastomoses; slightly longer than broad (largest width measured across mesoscutum on the level of the base of tegulae), with very few short, white setae. Notauli complete, deep, distinctly impressed, slightly converging at posterior end, with transverse rugae on bottom; anterior parallel and parapsidal lines hardly traceable in polished smooth areas; median mesoscutal line as short as longitudinal impression (sometimes hardly traceable); parascutal carina narrow. Mesoscutellum quadrangular, broader in posterior 1/4, longer than broad, only very slightly overhanging metanotum, uniformly dull, rugose, with irregular strong rugae, areas between rugae smooth, shiny; scutellar foveae slightly ovate or transverse, occupying 1/3–1/5 length of mesoscutellum, with smooth, shiny bottom, with elevated narrow, smooth median carina, separating foveae; foveae absent or very indistinct in some paratypes. Mesopleuron reticulate in upper half, with numerous transversely orientated delicate striae (rugae) medially, especially in anterior half; mesopleuron coriaceous ventrad to median transverse rugae, with more dense white setation; acetabular carina delimiting very narrow area; dorsal axillar area narrow, coriaceous to rugose, with some setae; lateral axillar area smooth, shiny, with some setae and rugae; subaxillular bar smooth, shiny, posteriormost part narrower than height of metanotal trough; postalar process with parallel delicate striae; metapleural sulcus reaching mesopleuron in upper third of its height. Metascutellum uniformly coriaceous, metanotal trough smooth, shiny, with some short, white setae; ventral impressed area nearly as high as height of metascutellum, smooth, with distinct longitudinal striae; central propodeal area smooth, shiny, without or with very few irregular, delicate wrinkles, lateral propodeal carinae distinct, curved outwards in posterior third; lateral propodeal area rugose, with dense, long, white setation. Nucha very short, smooth, shiny, without irregular wrinkles and rugae.

Tarsal claws simple, without basal lobe. Forewing longer than body, hyaline, with distinct, long, dense ciliation on margin, radial cell 3.7 times longer than broad; R1 nearly straight, Rs reaching wing margin and for a short distance following margin; areolet large, triangular, closed and distinct. Rs+M distinct throughout, reaching basalis somewhat posterior to middle.

Metasoma as long as head+mesosoma or slightly shorter, slightly longer than high in lateral view; 2nd metasomal tergite occupying more than half length of metasoma in dorsal view, without setae laterally, all subsequent tergites without setae, smooth, shining. Narrow posterior band on 2nd metasomal tergite and all subsequent tergites entirely uniformly, densely, minutely punctured. Ventral spine of hypopygium very short, prominent part as long as broad, with sparse, long white subapical setation, extending far beyond apex of spine, with many long setae ventrally. Body length 2.3–2.8 mm (n=20).

Gall ( Figs 54–56 ). The gall is a swelling of branches and twigs, usually located in middle of twig, not apically; sometimes swellings at joints of twigs; up to 6.0 cm long, 1.2–1.5 cm in diameter, coloured the same as the bark of twigs. When the gall mature, tissues hard, lignified. Larval chambers (up to 14 mm in length and 3–5 mm in diameter) arranged perpendicularly to main axis of gall, radiating from center of twig toward gall surface, reaching to 2– 3 mm from surface ( Fig. 56 ).

Biology. Only the asexual generation is known, inducing stem swelling-like galls on Quercus glauca . Mature galls were collected in late October, adults emerged under laboratory conditions the following spring.

Distribution. Taiwan: currently known from Nantou County, Lienhuachih Forest Research Centre only ( Fig. 57 ).

Comments. The genus Plagiotrochus includes 15 Western Palaearctic species ( Pujade-Villar & Ros-Farré 1998; Pujade-Villar et al. 2000; Nieves Aldrey 2001; Melika et al. 2010). Only three Eastern Palaearctic species have been described: P. semicarpifoliae ( Cameron) from the NW Himalayas, known to induce acorn galls on Q. semicarpifolia Smith ( Bellido et al. 2000) , and P. smetanai Melika & Pujade-Villar and P. follioti Pujade-Villar & Melika , both from Nepal ( Melika et al. 2009). Plesiomorphic traits of P. semicarpifoliae ( Cameron) , known from the Himalayan area, and the herein described new species from Taiwan, suggest a Southeast Asian origin for Plagiotrochus , with species from the Mediterranean region probably being derived and representing a secondary radiation ( Melika et al. 2010). On the basis of molecular data, Plagiotrochus glaucus does not seem to form a monophyletic group with Western Palaearctic Plagiotrochus species but rather appears plesiomorphic relative to the Mediterranean species (J. Nicholls, unpublished data).

Figures

FIGURE 57. Current distribution of Andricus songshui, A. pseudocurvator and Plagiotrochus glaucus (figure from http: // www. google. com / earth /,). The white dot represents the location where A. songshui and A. pseudocurvator occur together (Renai Township, Nantou County), the blue dot represents another site where A. pseudocurvator is known to occur (Heping Township, Taichung County), and the red dot shows the type locality of P. g l a u c u s (Nantou County, Lienhuachih Forest Research Centre).

FIGURES 39 – 44. Plagiotrochus glaucus, new species, female: 39 – 43, head: 39, anterior view, 40, dorsal view, 41, posterior view, 42, clypeus and lower face, anterior view. 43, mouthparts and postgenal bridge, posterior view. 44, antenna.

FIGURES 45 – 50. Plagiotrochus glaucus, new species, female: 45, mesoscutum, dorsal view, 46, mesoscutellum, dorsal view, 47, pronotum and propleuron, anterior view, 48, mesosoma, lateral view, 49, metascutellum and propodeum, posterodorsal view, 50, hind tarsal claw.

FIGURES 51 – 56. Plagiotrochus glaucus, new species, female: 51, forewing, 52, metasoma, female, lateral view, 53, ventral spine of hypopygium, lateral view. 54 – 56, gall (photos by J. Nicholls).