mayfly

American  

[mey-flahy] / ˈmeɪˌflaɪ /

noun

plural

mayflies

1. 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.

2. Angling. Also May fly an artificial fly made to resemble this insect.

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mayfly British  

/ ˈmeɪˌflaɪ /

noun

1. 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 an artificial fly resembling this

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Etymology

Origin of mayfly

First recorded in 1645–55; May + fly ¹

Example Sentences

"In some cases we've got a 90% reduction in one particular mayfly species and also in one particular caddisfly, and a 30% reduction in two other mayfly species."

From BBC • Mar. 10, 2026

Crappie are slow due to the mayfly hatch and should return to normal numbers in 2-3 weeks.

From Washington Times • Jul. 8, 2020

The Stroud Water Research Center in Pennsylvania, where Jackson is based, has a long tradition of testing water quality impacts on mayfly larvae.

From Scientific American • Dec. 6, 2018

Out of Sight, in the meantime, is a mayfly that appears briefly — this year in an old furniture building at 115 S. Jackson St., plus the building next door.

From Seattle Times • Aug. 2, 2017

I am going to make my mayfly life count for something.

From "The Cruel Prince" by Holly Black