Definition of "mayfly" [mayfly]

• Any of various fragile winged insects of the order Ephemeroptera that develop from aquatic nymphs and live in the adult stage no longer than a few days. Also called dayfly, shadfly. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "A Wisconsin mayfly hatch shows up on radar like a storm."
• "Another important and widespread early-spring mayfly is the larger March brown, which hatches from late morning to early afternoon."
• "In March and early April, the bluewing olive, or Baetis, mayfly is common throughout trout country."