Key to Caenis spp.
Couplet 3
5. First five or six tergites with blackish grey markings. Penis-lobes of male truncate (fig 16). Exp. 8.5-11 mm.

6. Only first three tergites with greyish markings. Penis-lobes of male with a wide excision between them (fig 17). Exp. 6.5 mm.