Mayflies
Ephemeroptera

Ephemeroptera is a group of 2,000 insect species commonly known as mayflies. They are known for their extremely short life spans and emergence in large numbers in the summer months.

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A cream-colored mayfly stands on a rock, its two long tails curving upward in an arc.
Mayflies like the giant mayfly have large compound eyes and two or three long, threadlike tails. (Photo courtesy of bwood708/iNaturalist CC BY-NC)

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Appearance

Winged mayflies have large compound eyes, short, bristlelike antennae, and functionless mouthparts and digestive tracts. Their membranous wings include a large, triangular front pair and a much smaller, rounded hind pair. In a few species, the hind pair is extremely reduced or absent.

Feeding

Some species are carnivorous, but the majority of nymphs feed on algae, higher plants, and organic decaying material. Nymphs are devoured in turn by many carnivorous animals, especially fishes.

Predators

Mayfly eggs are eaten by snails and by caddisfly larvae. The nymphs may be eaten by fish, frogs, birds, flies, or water beetles.

Reproduction and life cycle

Mayflies undergo incomplete metamorphosis. Their life cycle includes four stages – egg, nymph, subimago and adult (imago). Most species produce one or two generations per year.

Did you know?

  • Other common names for the winged stages are shadfly, sandfly, dayfly, fishfly, and drake.
  • The aquatic immature stage, called a nymph or naiad, is widely distributed in freshwater, although a few species can tolerate the brackish water of marine estuaries.
  • The existence of mayflies in a stream is a good indicator of water quality.

Sources and additional information

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