Platygaster urniphila Matsuo & Yamagishi

Matsuo, Kazunori, Fujii, Tomohisa, Tokuda, Makoto, Ganaha-Kikumura, Tomoko, Yukawa, Junichi & Yamagishi, Kenzou, 2018, Descriptions of two new species of Platygaster Latreille that attack gall midges (Diptera, Cecidomyiidae) with notes on their biology (Hymenoptera, Platygastridae), ZooKeys 754, pp. 113-125 : 117-121

Platygaster urniphila Matsuo & Yamagishi sp. n.

Etymology.

The specific name, urniphila, is derived from the jar-shaped gall of Rhopalomyia longitubifex .

Type material.

Holotype: Female, emerged on 2-4 April 2014 from a globular-jar shaped gall of Rhopalomyia longitubifex on Artemisia indica var. maximowiczii collected by K. Matsuo and Y. Matsuguma on 9 November 2013 from Chojabaru, Kokonoe, Oita, Japan. Paratypes: 1 female and 1 male, same data as holotype. 3 females, emerged on 31 March 2008 from a globular-jar shaped gall of Rhopalomyia longitubifex on Artemisia indica var. maximowiczii collected by K. Matsuo on 8 December 2007 from Jizoubaru, Kokonoe, Oita, Japan. 2 females, emerged on 8 April 2008 from a globular-jar shaped gall of Rhopalomyia longitubifex on Artemisia indica var. maximowiczii collected by K. Matsuo on 2 March 2008 from Chojabaru, Kokonoe, Oita, Japan. 2 females, emerged on 13 April 2008 from a globular-jar shaped gall of Rhopalomyia longitubifex on Artemisia indica var. maximowiczii collected by N. Wachi on 12 April 2008 from Kuju, Taketa, Oita, Japan. 5 males, emerged in April 2016 from a globular-jar shaped gall of Rhopalomyia longitubifex on Artemisia indica var. maximowiczii collected by K. Matsuo and Y. Matsuo on 24 March 2016 from Tano, Kokonoe, Oita, Japan.

Description.

FEMALE (Fig. 10). Body length 1.1-1.3 mm. Head, mesosoma, and metasoma black. A1-A2 black; A3-A10 dark brown to black. Fore wing slightly infuscate. All legs dark brown to black.

Head in dorsal view, 1.7-1.8 times as wide as long, 1.0-1.1 times as wide as mesosoma; occiput with weak transverse striations; vertex between ocelli smooth (Fig. 11); POL: OOL: LOL = 2.4: 1.0: 1.0. Head in frontal view 1.2-1.3 times as wide as high; frons smooth medially (Fig. 12), sometimes with fine striations; gena reticulate. A1 5.7-5.9 times as long as wide, 0.7-0.8 times as long as height of head; A2 1.5-1.6 times as long as wide; A3 quadrate; A4-A6 subquadrate, 1.1-1.2 times as long as wide; A7-A9 1.1-1.3 times as long as wide; A10 1.4-1.6 times as long as wide (Fig. 13).

Mesosoma as high as wide, 1.3-1.4 times as long as wide; sides of pronotum broadly smooth which is sometimes with extremely fine striae, smooth along posterior margin (Fig. 15); mesoscutum smooth in posterior half; notauli indicated in posterior half (Fig. 16); posterior margin of median lobe of mesoscutum not reaching base of mesoscutellum, with numerous long setae laterally; scuto-scutellar groove smooth and bare; mesoscutellum distinctly convex, smooth and covered with long hairs except median glabrous area (Fig. 17); mesopleuron with two setae anteriorly, with a coriaceous area below tegula; mesopleural carina absent; mesofurcal pit present; metapleuron pilose, sparse in dorsal one-third; propodeal carinae widely separated, parallel. Fore wing approximately 2.4 times as long as wide; marginal cilia approximately 0.1 times as long as width of fore wing. Hind wing approximately 5.3 times as long as wide, with two hamuli; marginal cilia approximately 0.2 times as long as width of hind wing.

Metasoma as long as head and mesosoma combined; T1 evenly crenulated, 1.7-1.8 times as wide as long, 0.2-0.3 times as long as T2; anterior margin of T2 weakly produced and overlapped T1; T2 weakly striated in basal half, with shorter striae medially (Fig. 18); T2-T5 with a band of shallow punctuation along posterior margin; T3-T5 with a row of setae which is broken medially; T6 with a setal row which is sometimes sparse medially, smooth.

MALE. Differs from the female as follows: Body length 1.1 mm. Antenna with erect setae; A4 distinctly widened; A5-A9 quadrate (Fig. 14). Metasoma approximately 0.8 times as long as head and mesosoma combined, obtuse at apex.

Differential diagnosis.

Platygaster urniphila can be distinguished from P. urnicola Yamagishi, a Japanese species, based on the following characteristics: mesopleuron with a few setae anteriorly (glabrous in P. urnicola ); posterior margin of median lobe of mesoscutum not reaching base of mesoscutellum (reaching base of mesoscutellum in P. urnicola ). Platygaster gifuensis was described based on a single male from Japan, from which P. urniphila can be distinguished by having A5-A9 quadrate (approximately 1.5 times as long as wide in P. gifuensis ). Platygaster urniphila is quite similar to P. sublongicornis Buhl because they share the following morphological characteristics: vertex between ocelli smooth; frons smooth medially; mesopleuron with a few setae anteriorly, with a coriaceous area below tegula; mesoscutellum distinctly convex; T2 weakly striated in basal half, with shorter striae medially. However, Platygaster urniphila can be distinguished from P. sublongicornis based on the following characters: A4-A5 subquadrate (distinctly elongate in P. sublongicornis ); OOL as long as LOL (1.6 times as long as LOL in P. sublongicornis ); sides of pronotum smooth along posterior margin (smooth along anterior and posterior margins in P. sublongicornis ); hind wing approximately 5.3 times as long as wide (4.5 times in P. sublongicornis ).

Biological notes.

Platygaster urniphila is an egg-larval gregarious parasitoid of Rhopalomyia longitubifex that induces axillary bud galls on Artemisia indica var. maximowiczii in Japan ( Yukawa and Masuda 1996; Ganaha et al. 2007). Gall polymorphism has been found in R. longitubifex : long jar-shaped, jar-shaped, and globular jar-shaped (see figures 1-5 of Ganaha et al. 2007). At present, P. urniphila has been reared only from globular jar-shaped galls. Various sorts of galls induced by Rhopalomyia spp. have been found on Artemisia spp. (e.g. Yukawa and Masuda 1996; Yukawa 2014; Gagné and Jaschhof 2017), but P. urniphila has been reared only from galls of Rhopalomyia longitubifex on A. indica var. maximowiczii in Japan. Future intensive studies are needed to confirm the host range of P. urniphila .

Leiby and Hill (1924) noted that Platygaster vernalis , a polyembryonic species, occasionally laid male and female eggs into a single host egg. Thus, P. vernalis has both polyembryonic and gregarious reproductive strategies. Our rearing experiments indicated that P. urniphila is a gregarious parasitoid because males and females were reared from a single host larva (Table 1). To confirm polyembryonic reproduction by P. urniphila , we need histological survey or MIG-seq analysis ( Suyama and Matsuki 2015) that discriminate individuals originated from clonal division and sexual reproduction.