mayfly

mayfly, any insect of the order Ephemeroptera, so named because the adults live for a short time, often only a single day, during which they molt twice, mate, and lay their eggs in freshwater. The adults are medium to large, shiny, slender insects with two pairs of fragile, transparent, many-veined wings, and two or three long threadlike tails. The long forelegs of the male are used to clasp the female during the mating flight. Mayflies, also called June bugs, shad flies, and salmon flies, emerge by the thousands from streams, ponds, and lakes at twilight in the early spring; the males form large mating swarms and when a female flies into the swarm she is seized by a male and the two depart to mate. Mayflies lack fully developed mouthparts and do not feed. The insect undergoes incomplete metamorphosis, the egg hatching directly into an aquatic naiad, or nymph, with chewing mouthparts, which passes through some 20 nymphal stages over a period of two years or more, feeding on algae and diatoms and breathing oxygen taken directly from water by gills. It emerges from the water to transform into a subadult phase known as the subimago, unique among insects, in which it has wings and can fly but has immature legs, tail, and reproductive system. Adult mayflies are an important food source for many animals; several fishing flies are modeled after them. Mayflies are classified in the phylum Arthropoda, class Insecta, order Ephemeroptera.

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mayfly

Any insect of the order Ephemeroptera, found around streams and ponds. The approximately 2,000 species are up to 1.6 in. (4 cm) long, have triangular membranous forewings, smaller round hind wings, and two or three long, threadlike tails. Wings are held vertically when at rest. Chewing mouthparts in the aquatic larvae are vestigial in the adult, which lives just long enough to mate and reproduce. Males “dance” in large swarms to attract females. The adult's entire life span is usually only a few hours (though at least one species lives as long as two days), and poets have used the mayfly as a symbol of life's ephemeral nature.

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mayfly

1. 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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mayfly [′mā‚flī]

(invertebrate zoology)

The common name for insects composing the order Ephemeroptera.