Evaluation of Mayfly Species Originally Described as Baetis Leach (Ephemeroptera: Baetidae) from California

Eight species of mayflies described in Baetis Leach from California are evaluated for validity, generic classification, and distribution. Taxonomic status quo is maintained for the southwestern Baetis adonis Traver [ = B. sp. A Morihara and McCafferty, = B. caelestis Allen and Murvosh], B. devinctus Traver [synonym of Diphetor hageni (Eaton)], and B. leechi Day [synonym of Fallceon quilleri (Dodds)]. Baetis alius Day is shown to be common in the northwestern U.S.A. and somewhat variable but distinctive as larvae; B. moqui Wiersema, Nelson and Kuehnl is shown to be a junior synonym of B. alius, new synonym. Baetis diablus Day is correctly placed to genus but remains unknown as larvae and has been rarely taken only in California; it is possibly a variant of B. tricaudatus Dodds. Baetis palisadi Mayo is correctly placed to genus, and based on discovered larvae has diagnostic mandibles and labial palpi among rhodani group species; it is apparently endemic to California and of environmental concern. Baetis piscatoris Traver is correctly placed to genus, relatively common in California, and based on discovered larvae is the only known rhodani group species with elongate gills. Baetis sulfurosus Day belongs in Fallceon Waltz and McCafferty, as evidenced by discovered larvae; it is also a junior synonym of the western F. thermophilos (McDunnnough), new combination, new synonym, and is distinct from western congeners by size and color pattern of larvae, and hindwings and subgenital plate of adults.