- 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
WordReference Random House Learner's Dictionary of American English © 2016
- Insectsan insect with large clear wings and a threadlike tail.
n., pl. -flies.
- InsectsAlso called shadfly. any insect of the order Ephemeroptera, having delicate, membranous wings with the front pair much larger than the rear and having an aquatic larval stage and a terrestrial adult stage usually lasting less than two days.
- Also,May′ fly′. [Angling.]an artificial fly made to resemble this insect.
- May + fly2 1645–55