Isoperla flavescens Zhiltzova & Potikha 1986

Isoperla flavescens Zhiltzova & Potikha, 1986 (in Potikha & Zhiltzova 1986) Figs. 28–34 Material examined. Russia, Far East, Khabarovsk Krai: 1♂, Anyuisky National Park, Tormasu River, Anyui R. basin, Amur R. basin, 21.06.2018, coll. N. Yavorskaya; Primorsky Krai: 7♂ 7♀, Lazovka River, Partizanskaya R. basin, below the pass, under the bridge, 13.06.1998, coll. V. Teslenko; 9♀, Malinovka River, Ussuri R. basin, Amur R. basin, 10 km above the Pozhiga village, highway, 16.06.1998, coll. V. Teslenko. Egg. The egg of I. flavescens is described here for the first time. Shape oval, symmetrical with anterior and posterior poles broadly rounded (Figs. 28‒29) and a concave cross-section (Fig. 32). Length of 287–302 µm and a width at the equator of 200–217 µm (n=4). Collar well developed, with irregular longitudinal ridges extending onto the shoulder; shoulder contoured with a ring; rim incised and flanged (Figs. 29, 31–32). Anchor mushroom-shaped, with small grouped globular bodies covering the entire surface of the anchor evenly (Figs. 28, 30). FCIs near collar range from pentagonal to hexagonal (Fig. 32). Chorion covered with hexagonal FCIs with thick elevated ridges (Figs. 28‒29, 32–34); floors covered with deep pits, their number not exceeding 9–13 (Figs. 33‒34). Micropylar row visible near anterior ¼ (Fig. 29). Micropyles located near ridges and surrounded with rosettes of FCIs (Figs. 29, 34). Micropylar canals smaller than in other species; orifices and sperm guides weakly visible (Fig. 34). Distribution. East Asian species with limited distribution in the south of the Russian Far East (Jewish Autonomous Region, Khabarovsk Krai, and Primorsky Krai). South Korea (Kim et al. 1998). China (Changbai Mountains) (Huo et al. 2022).