Ephemera danica can reach an imago size of 15–20 mm (0.6–0.8 in) in males, while females are larger, reaching 16–25 mm (0.6–1.0 in). This mayfly, with its characteristic markings and three tails (Cerci), is the most commonly seen of British Ephemeridae. Imago wings are translucent with dark veining, while in subimago they are dull and yellowish with brown veins. Moreover forelegs and the tails of the spinners are very much longer than in duns.[1] Mouthparts are non-functional, as adults do not feed.