Also 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.
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