In the genus Ephoron of Japan three species are recognized: E. shigae (Takahashi), E. limnobium sp.nov., and E. eophilum sp.nov. This study includes a key to the species, a description of each species, and maps of species distributions.

The species of the genus Isonychia Eaton, 1871 (Isonychiidae) of East Palaearctic are revised. Two subgenera, Isonychia s.s. and Prionoides Kondratieff et Voshell, 1983, are represented in the Palaearctic. New species and subspecies of Isonychia s.s. are described: I. sexpetalasp. nov., I. ussurica sibiricasubsp. nov., I. concoloriasp. nov., I. crassiusculasp. nov., and I. vshivkovaesp. nov. with subspecies I. vshivkovae vshivkovae and I. vshivkovae sinitshenkovaesubsp. nov. A new species group japonica, with three species (I. crassiuscula, I. vshivkovae, and I. japonica), is recognized on the basis of adult and larval characteristics. The name Isonychia hainanensis She et You, 1988 is synonymized with Isonychia ignota (Walker, 1853) syn. nov.

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The Japanese mayfly genus Cincticostella is taxonomically revised. The fbur currently recognized species are Cincticostella (Cincticostella) elon.uatula (McLachlan, 1875) (=okumai Gose, 1980, syn. nov.), C. (C.) levanldovae (Tshernova, 1952), C. (C,) ntgra (Ueno, 1928>, and C. (C,) orientalis (Tshernova, 1952) (=tshernovae (Bajkova, 1962). The lectotype and paralectotypes of Eiphemerella nigra are designated from the syntypes of Uene. Specimens treated as C. (C.

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