Oyamia nigribasis Banks 1920

Oyamia nigribasis Banks, 1920 Figs. 69−75 Material examined. Russia, Far East, Amurskaya Oblast: 1♀, Bureya River near Novobureysk, left bank, Amur River basin, 12.07.2012, coll. V. Teslenko; Jewish Autonomous Oblast: 1♀, Bastak Nature Reserve, Glinyanka River, light trap, 11.07.2018, coll. T. Vshivkova; Primorsky Krai: 4♀, Pasechnaya River, Kievka River basin, Lazo settlement, 24.07.2005, coll. Yu. Sundukov; 12♂, 7♀, Komissarovka River near Dvoryanka village, Khanka Lake basin, 25.06.2015, coll. V. Lyubaretz; 5♂, 11♀, Shumnaya River, Ussuri River basin, Amur River basin, near Shumnyi settlement, 26.06.2017, coll. V. Lyubaretz; 1♂, 1♀, Bolshaya Ussurka River, Amur River basin, Melnichnoe village, 7.07.2013, coll. V. Lyubaretz. Egg. Oval but slightly asymmetrical (Figs. 69, 74), dark brown, total length 446−390 μm, equatorial width 317−291 μm (n=3). Collar short, stalked, rim flanged, and irregularly incised; sides of collar with irregularly spaced ridges reaching the shoulders and forming a single row of prolonged, hexagonal, smooth, and shallow cells (Figs. 69, 71, 74). Anchor is umbrella-like; the surface is composed of hexagonal units with globular bodies (2–9) grouped inside and distributed over the whole area of the anchor plate (Fig. 70); the edge of the anchor plate has a row of triangular projections bearing the single globular bodies (Fig. 70). The cleaned chorion is smooth, with indistinct follicular cell impressions over the whole surface (Figs. 69, 72). The structure on the extrachorion membrane with hexagonal FCI’s bearing a few (2−4) large adhesive mushroom bodies over each follicle cell impression (Figs. 74−75). The micropylar line is closer to the anterior pole; micropylar canals are tunnel-shaped, long, and slightly slanted; sperm guides open; orifices have slightly raised rim (Figs. 69, 73). On the extrachorion layer, micropylar orifices are surrounded by rosettes of FCI’s that resemble flowers (Fig. 75). Comments. The egg of O. nigribasis is generally similar to that of O. lugubris (McLachlan, 1875), but the chorionic surface of that species at the shoulder area is covered with two rows of hexagonal, smooth, and deep cells with raised walls (Isobe & Uchida 2009). Distribution: East Asian mainland species with distribution limited to the south of the Russian Far East (Amurskaya Oblast, south Khabarovsk Krai, and Primorsky Krai), China (Huo et al. 2022), North Korea (Zwick 1973), and South Korea (Stark 2010).