Osmylus decoratus Nakahara 1914

Osmylus decoratus Nakahara, 1914 (Figures 4, 14B, K) Osmylus decoratus Nakahara, 1914, p. 514; Kuwayama, 1962: 343; Hayashi, 2005: 389; Winterton et al., 2019: 38. Type locality: Japan (‘Kusakimura, Prov. Hrima’, ‘Prov. Wakasa’ and ‘Prov. Chikugo, Kiushiu’). Osmylus (Osmylus) decoratus Makarkin, 1985: 41; 1990: 31, 1995: 44; Sekimoto and Yoshizawa, 2011: 13; Dobosz et al., 2019: 9. Plethosmylus decoratus Krüger, 1915: 76; Hirai, 1955: 269; 1956a: 155, 1956b: 57; Nakahara, 1960: 34. Diagnosis Head brown; vertex dark, with an X-shaped black marking. Pronotum dark brown. Fore wing gradate series area to apex, M and Cu area and inner margin with dark brown markings. Process of male tergum 9 very tiny; tubercles of gonocoxites 9 indistinct, in ventral view ovoid. Redescription Head width 2.9 mm; fore wing length 22.9 mm; hind wing length 20.5 mm. Head. (Figure 4C) Dark brown. Vertex dark, strongly convex; an X-shaped black marking present. Ocelli distinct, with three triangularly arranged yellow spots. Antennae black, flagellum filiform. Frons dark brown. Clypeus and labrum brown. Mandibles basally brown, distally dark brown. Thorax. (Figure 4B) Pronotum almost black with brown markings. Meso- and metanotum black, covered with many brown setae. Legs. Long and slender, pale yellow, covered with short setae. Tibia nearly twice as long as femur, tarsomere 1 relatively longer, nearly as long as entire length of tarsomeres 2–4; pretarsal claws curved. Metatibia longer than that of fore- and midlegs. Wings. Ovoid and broad, hyaline. Pterostigma dark brown alternating with pale. Fore wing outer gradate series area to apex and Cu area with irregular brown markings, along inner gradate series with indistinct markings, fore wing inner margin with intermittent brown markings; costal space broad basally, subcostal veinlets basally connected by some short oblique crossveins; RP with 12–13 branches; RP1 originating near origin of RP, M fork close to origin of RP1; RP with two distinct gradate series, CuP with numerous crossveins; A1 and A2 with pectinate branches and crossveins. Hind wing subcostal veinlets without interlinked crossvein; outer gradate series and apex with a dark dot. Abdomen. Dark brown, covered with yellowish-brown setae. Male genitalia (Figure 4D, E): Tergum 8 long; callus cerci relatively large and ovoid. Process of male tergum 9 tiny, distally concave. Gonocoxites 9 slightly sclerotised distally, tubercles of gonocoxites 9 indistinct, in ventral view ovoid; gonocoxites 10 (Figure 14B) curved arcuately. Female genitalia (Figure 4F, G): Sternum 7 with a small process, subtriangular in ventral view; gonocoxite 8 small, curved ventrally; tergum 9 without branch. Gonocoxite 9 as a slender fusiform structure; in ventral view anterior angle extremely extended, acutely tapering. Ectoproct subtriangular in lateral view. Spermatheca simple and ovoid (Figure 14K). Material examined CHINA: 1♂, Inner Mongolia, Tongliao [通辽市], Dqainggou [大青沟], 180 m, 24 August 2022, leg. Xingyang Qian (CAU); 1♀, Heilongjiang, Muling [穆棱市], Gonghe Town [共和 乡], Liufeng Mountain [六峰山], 450 m, 12 July 2022, leg. Xiaoshuan Bai (CAU); 1♀, Jilin, Yanbian, Wangqing County [汪清县], Jiguan Township [鸡冠乡], Cilaoyagou Village [刺老 芽沟村], 461 m, 3 July 2023, leg. Xingyue Liu (CAU); 2♂ 4♀, Jilin, Baishan, Fusong County [抚松县], Lushuihe Town [露水河镇], 764 m, 12 July 2023, leg. Leran Cao (CAU). Distribution China (Jilin, Heilongjiang, Inner Mongolia), Japan (Hokkaido, Honshu), Russia (Kuanshir Island). Remarks This species can be easily distinguished from other species by the presence of an X-shaped marking on head and numerous brown spots on fore wings.