Eurystylus Stal 1871

Genus Eurystylus Stål, 1871

Eurystylus Stål, 1871: 671 (new genus), type species by monotypy: Eurystylus costalis Stål, 1871: 671; Yasunaga, 2001: 233 (diagnosis); Zheng et al., 2004: 271 (diagnosis, key to Chinese spp.); Schuh, 2002 –2013 (online catalog); Yasunaga et al., 2017: 305 (diagnosis); Oh et al., 2018: 473 (faunal list); Aukema, 2018 (online catalog).

Diagnosis: See Yasunaga et al. (2017).

Distribution. Known from the Old World, mainly subtropical and tropical zones; most species occurring in the Ethiopian and Oriental regions.

Discussion. As argued by Yasunaga et al. (2017), Eurystylus is easily separable from related genera by the tumid, box-like body shape; generally grayish, brownish or blackish basic coloration; thick, flattened antennal segment I; a pair of fuscous, triangular, velvety marks (= clustered micro-pilosity, cf. Figs. 1D–E, 10K–L, N–O) at lateral corner on the frons (along inner margin of eye); paired dark ocellate (or sometimes oblong) spots on pronotal disk (cf. Fig. 1A, D); thick collar, elongate, more or less inflated scutellum; and short genital segments (male pygophore and female segments VIII and IX). A combination of these characters enable to distinguish Eurystylus from superficially similar taxa known from the eastern Asia and Oriental Region (e.g., Eocalocoris, Eurystylopsis Poppius, Heteropantilius Zheng & Liu, Miyamotoa Yasunaga and Taiwanocapsus n. gen.). A new species described below, E. yixuanae n. sp., uniquely has a yellow-green basic coloration and smooth frons that lacks the black, clustered micro-pilosity; however, the male and female genitalic structures (e.g., possession of four homologous lobal sclerites on the vesica as in Fig. 5, FL, ML, PL and TL) undoubtedly represent diagnostic characters shared by other Eurystylus species (cf. Yasunaga et al., 2017).

In Taiwan, five Eurystylus congeners are now known: E. coelestialium (Kirkaldy, 1902), E. jingfui Yasunaga, Nakatani & Chérot, 2017, E. sauteri Poppius, 1915, E. ryukyus Yasunaga, Nakatani & Chérot, 2017 and E. yixuanae n. sp. The following key (updated from Yasunaga et al., 2017) will aid in correct identification of each species.

1. Body widely yellow-green; frons uniformly pale olive green, immaculate.......................... E. yixuanae n. sp.

- Basic coloration brownish or blackish; frons at inner margin of each eye with fuscous, triangular, velvety mark (or clustered micro-pilosity)....................................................................................... 2

2. Pronotum almost entirely fuscous, without noticeable pale portion or macula............................... E. jingfui

- Pronotum grayish brown, pale brown, or brown, usually with a pair of darker spots on disk........................... 3

3. A pair of dark spots on pronotum clearly surrounded by pale margin................................. E. coelestialium

- A pair of dark spots obscure, ovoid, narrowed (Fig. 1E–F) or sometimes obliterated................................ 4

4. Antennal segment III entirely dark, without pale base; paired spots on pronotum ovoid and comparatively clear.. E. ryukyus

- Base of antennal segment III always pale; paired spots on pronotum elongate and obscure, sometimes reduced or obliterated............................................................................................ E. sauteri