A Revision of the Genus Ephemerella (Ephemeroptera: Ephemerellidae) II. The Subgenus Caudatella1

The six known species of this subgenus include E. (C) orestes from Oregon and E. (C.) cascadia from Oregon and northern California, both of which, like E. (C.) edmundsi Allen, are known only from nymphs. Adults of E. (C) hystrix Traver are described for the first time. E. (C.) heterocaudata McDunnough (=E. columbiella McD., new synonymy) is polytypic, with E. (C.) h.californica occurring in the Sierra Nevada mountains of central and southern California, and E. (C.) h.circia in west-central Oregon. Keys are given to the nymphs and to the adults so far as known, and complete synonymies and distributions are included.