Ephemera (Sinephemera) shengmi Hsu, 1937

Figures 31–37

Material examined. Russia: Primorsky Krai, Ussuriysky district, Razdolnaya River, above Zarechnoe village, 04.08.2007, 2 ♀ adults, T. Tiunova; Khankaisky district, Lake Khanka, Przhevalsky spit, 12.08.2002, 10♀ adults, T. Tiunova.

Distribution. South of the Russian Far East, China.

The egg is oval (Figs 31–32, 35–36). Dimensions: 224.0–255.0 µm in length (239.9 µm) and 130.0–142.0 µm in width (136.3 µm). The extrachorion-adhesive layer is thin, 0.5–1.2 μm; therefore, the surface of the adhesive layer partially follows the sculpture of the chorion (Figs 31–32, 35). In the equatorial area, there are one to two micropyles per egg (Figs 31–32, 35).

Eggs are characterized by a linear-type micropyle (Koss and Edmunds 1974). In this type of micropyle, there is no sperm guide, and the micropylar canal is relatively short and protrudes over both the adhesive and chorion surfaces (Figs 31–32). The micropylar canal, tunnel-shaped with thick walls, is relatively short, 8–14 μm long and 7–10 μm wide (Fig. 33). The micropylar opening is nearly round, 3.5 μm wide and 3.0 μm high (Figs 33, 37). The sculpture of the chorion consists of discontinuous long and short ridged, curved, and broken filaments, the distribution and arrangement of which regularly cover the entire surface of the chorion (Figs 35–37).

Ephemera (Sinephemera) strigata Eaton, 1892

Figures 38–45

Material examined. Russia: Primorsky Krai, Khasansky district: Barabashevka River, below the Fish Hatchery, 4♀ adults, 10.06.2003, T. Tiunova; Barabashevka River, above the Fish Hatchery, 24.06.2021, 1♀ adult, T. Tiunova; Ryazanovka River, below the Okhotbaza, 11.06.2003, 3♀ adults, T. Tiunova.

Distribution. East Siberia, Far East Russia, Japan, Mongolia, Korea, China.

The egg has been described by Okazaki (1981, p. 9: fig. 6; 1984, p. 21: fig. 15) and Tojo & Machida (1998, p. 575: fig. 2). The authors write that the eggs of E. strigata and E. japonica are very similar in egg size and shape, in the thickness of the adhesive layer, in the structure of the chorion, and in the absence of micropyle.

According to our data, the egg is oval (Figs 38–39). Dimensions: 197.0–239.0 µm in length (215.2 µm) and 116.0–139.0 µm in width (126.6 µm). The extrachorion-adhesive layer covering the egg is presented as a thin membrane (Fig. 42). The adhesive layer is almost smooth (Figs 38–39, 41). There are one to two micropyles per egg in the equatorial area (Figs 38–39). The micropyle is of the “tagenoform type,” with a drop-shaped, poorly defined sperm guide, 14–18 μm long and 16–18 μm wide (Fig. 40). The micropylar canal is 9.8–15.6. µm long and 5.5–7.2 µm wide; the entrance to the micropylar canal is tunnel-shaped, with thick walls; it protrudes above the adhesive layer and chorion (Figs 40, 43). The micropylar opening is rounded to 2.5–3.0 µm wide and 2.5–2.9 µm high (Figs 43–44). The chorionic surface is finely wrinkled (Figs 43, 45).