Torymus sinensis Kamijo, 1982

Viciriuc, Ionela-Mădălina, Mitroiu, Mircea-Dan, Askew, Richard Robinson, Ris, Nicolas, Fusu, Lucian & Borowiec, Nicolas, 2023, Torymus sinensis and its close relatives in Europe: a multilocus phylogeny, detailed morphological analysis, and identification key, Arthropod Systematics & amp; Phylogeny 81, pp. 705-730 : 705

Torymus sinensis Kamijo

Chresonymy.

Torymus sinensis Kamijo, 1982: 505-507. Holotype ♀, Museum of the Institute of Zoology, Academia Sinica, Beijing, not examined. Type locality: Taliuchuang, Tsunhua, Hopei, China. - Torymus sinensis ; Ôtake 1987: 601-609 (compared with T. beneficus , illustrated): Izawa et al. 1992: 58-60 (compared with T. beneficus using allozymes); Grissel 1995: 287 (catalogued); Yara et al. 2000: 201-206 (compared with T. beneficus using morphology and allozymes); Yara 2004: 428-432 (compared with T. beneficus using morphology and DNA); Yara 2006: 18-19 (compared with T. beneficus using DNA); Yara and Kunimi 2009: 278-279 (compared with T. beneficus using DNA); Quacchia et al. 2014: 107, 110 (interspecific crosses); Ferracini et al. 2017: 447, 449-450 (interspecific crosses); Montagna et al. 2019: 334-341 (compared with T. beneficus using DNA); Pogolotti et al. 2019: 5-6 (compared with Torymus spp. using DNA); Viviani et al. 2019: 5-7 (compared with Torymus spp. using DNA); Matsuo 2020: 403, 408, 433-434 (compared with T. beneficus , keyed, illustrated); Matsuo et al. 2021: 457-459 (compared with T. beneficus using morphology and DNA); Gil Tapetado et al. 2022: 106-110 (compared with T. cyaneus and T. notatus using DNA); Viciriuc et al. 2021: 5-13 (compared with T. beneficus , taxonomy); Gil-Tapetado et al. 2023: 6-9 (compared with T. beneficus and T. notatus using DNA, interspecific crosses).

Diagnosis. Both sexes: Head (Fig. 12A, B ) and mesosoma (Fig. 12E, F ) from green to blue, occasionally with coppery reflections; gaster usually concolorous with mesosoma (Fig. 7A, B ), sometimes mostly brown with green to blue reflections in smaller specimens, where body colour is generally less metallic and darker; scape yellowish brown, darker apically, sometimes completely darkened. Fore wing hyaline with brown venation (Fig. 12C, D ). Coxae and femora from dark brown to concolorous with mesosoma; hind tibia less strongly darkened, usually more or less infuscate but not dark brown, occasionally yellow; fore and mid tibiae mostly yellow. In smaller individuals the body colour is less metallic and darker. Scutellum immediately anterior of the frenal line alutaceous, more strongly sculptured or even strigose on the anterior half, frenum smooth and bare, rarely with weak striae posterolaterally; in some small specimens scutellum almost completely smooth. Propodeum with a pair of distinct and curved submedian carinae (Fig. 12G, H ), present irrespective of body size; propodeum with or without smaller additional carinae laterad of the central pair. Female: ovipositor index 1.2-2.7.

Remarks.

In this study, we analysed several hundred specimens of T. sinensis collected from different geographical areas in both Europe and Asia and the most variable character of European individuals was found to be the body colour.

Besides the characters given in the key, females of T. sinensis differ from those of T. affinis that sometimes can have a shorter ovipositor, in having the hind coxa bare in basal half (hind coxa with short setae in basal half in T. affinis ). From T. notatus , besides the more obvious characters used in the key, T. sinensis differs in some less obvious ratios obtained in the LDA analysis: width of the first funicular segment and length of greatest spur for females, and width of the first funicular segment and length of the short spur for males (Table S6).

However, the closest species to T. sinensis (Fig. 7A, B ) is T. beneficus (Fig. 7C, D ), which is endemic to Japan. The two can be differentiated using the ratio of antennal flagellum (combined length of anellus, funiculars and clava) to head width ( Kamijo 1982), and ovipositor sheath and hind tibia ( Matsuo 2020). Differences in the length of individual funicular segments were also found by Viciriuc et al. (2021), but they failed to find a difference when using the entire length of the flagellum. Presumably this is because it is difficult to accurately measure the antenna which is usually more or less curved in dry mounted specimens. Our new measurements indicate that the ratio given by Kamijo (1982) is accurate. It is 1.22-1.34 in four female paratypes and 1.75-1.77 in four male paratypes of T. beneficus [repository and label details given in Viciriuc et al. (2021)], and 1.13-1.16 and 1.51-1.69 in eight females and two males of T. sinensis from China, respectively. For the European or Japanese specimens this ratio cannot be used because the values for the females correspond to both species (1.17-1.25 in four females from France) and for the males this ratio corresponds to T. beneficus (1.64-1.86 in five males). This confirms their intermediate morphology between T. sinensis and T. beneficus ( Viciriuc et al. 2021).

The length of the ovipositor comparatively with the mesosoma ( “thorax”) cannot be used as originally proposed by Kamijo (1982) when he described T. sinensis and used afterwards by many authors following Ôtake (1987). Even if T. beneficus has a comparatively shorter ovipositor than T. sinensis , the latter species is too variable, including in China, its original distribution area ( Yara 2004; Viciriuc et al. 2021). Recently, Matsuo (2020) proposed a separation based on the ovipositor index (the ratio between the length of ovipositor sheath and hind tibia). For the four female paratypes of T. beneficus this is 1.61-2.06 and for the seven females of T. sinensis from China it is 2.14-2.42. In Europe the interval of the ovipositor index overlaps that of the two species ( Viciriuc et al. 2021). Basically, only native T. sinensis and T. beneficus can be discriminated from each other, but not the specimens used for biological control in Japan or imported from Japan to Europe, due to their intermediate characteristics.

Teratological specimens.

During the morphological study of T. sinensis collected on D. kuriphilus we found a few specimens (two males and a female out of several hundred examined) that have malformations on the mesosoma. If such specimens are found in the future they could be misidentified, especially if the modifications are on the propodeum. The male with the molecular code 22204 (length 2 mm; Fig. 12I ), collected in San Lorenzo (France) in 2015, has the central part of the frenum rugose, and the propodeum has two pair of submedian carinae instead of one pair. The male 28598 (2.16 mm; Fig. 12J ), collected in St. Georges les Bains (France) in 2016, has teratological modifications in the structure of mesoscutum and mesoscutellum: the mesoscutal median lobe is transverse and has a U-shaped depression; the mesoscutellum has a longitudinal depression along midline and its posterior margin is strongly emarginated. The female 28629 (3.1 mm; Fig. 12K ), collected in Prigorieux (France) in 2016, has modifications in the structure of the pronotum, mesoscutum and scutellum: the pronotum has a median groove in its posterior half; the mesoscutal median lobe is transverse and has a U-shaped depression; the frenum has an unusual longitudinal notch; the posterior margin of the mesoscutellum is emarginated.

Biology.

Torymus sinensis is most frequently reared from galls of D. kuriphilus on Castanea crenata and C. molissima in Asia, C. dentata in North America, and C. sativa in Europe; with a low incidence it may be reared from other non-target gall wasps ( Ferracini et al. 2017; Gil-Tapetado et al. 2023).

The species has one generation per year. In southern France the adults start to emerge in mid-February and emergence continues to early-May, but some individuals emerge from June to August ( Borowiec et al. 2018). A diapause as larva of 12 months was identified in Italy in some cases ( Picciau et al. 2017).

Distribution.

Native to China and introduced to Japan ( Murakami et al. 1977), USA ( Rieske 2007), Italy ( Quacchia et al. 2008), France ( Borowiec et al. 2014), Spain ( Nieves-Aldrey et al. 2019), Croatia, Hungary, Slovenia ( Matošević et al. 2015), Portugal ( Amorim et al. 2022) and Turkey ( İpekdal et al. 2017).

Figures

Figure 7. Habitus for Torymus sinensis (A, B) and T. beneficus paratypes (C, D).

Figure 12. Torymus sinensis, head in frontal view: female (A), male (B); fore wing: female (C), male (D); mesosoma: female (E), male (F); propodeum: female (G), male (H); mesosoma in teratological specimens: male 22204 (I), male 28598 (J), female 28629 (K).