Key to Caenis spp. Couplet 47. Base of terminal antennae bristle conically dilated. Penis-lobes with a broad sinuous excision between them (fig 18). Exp. 7-9 mm.
8. Base of antennal bristle not conically dilated. Penis-lobes truncate with a narrow excision between them (fig 19). Exp. 8.5-15 mm.
