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Any of various delicate, winged insects of the order Ephemeroptera that develop from aquatic nymphs and in the adult stage live no longer than a few days and do not feed.
n, pl -flies
1. (Animals) Also called: dayfly any insect of the order Ephemeroptera (or Ephemerida). The short-lived adults, found near water, have long tail appendages and large transparent wings; the larvae are aquatic
2. (Angling) angling an artificial fly resembling this
n., pl. -flies.
any of numerous insects of the family Ephemeridae, with large transparent forewings and threadlike tails, living for a relatively long period as an aquatic nymph and only for two days or less as an adult.