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© John Pickering, 2004-2019 · 0
Click here for Mayfly checklist in the Great Smoky Mountains.

Mayflies are one of the most important herbiverous invertebrate aquatic insects. They are insects of moderate size with an incomplete metamorphosis. The immature stage is aquatic and the adult stage is very brief. Nymphs are adapted to diverse aquatic environments (Needham 1935). The key function of the adult is reproduction and dispersal. They do not feed and only live from 1-2 hours to 14 days at most (Elliott and Humpesch 1983).

The oldest living winged insects, dating "from the Carboniferous and Permian times," mayflies are one of the most important herbiverous invertebrate aquatic insects (Earthlife World of Insects). They are insects of moderate size with an incomplete metamorphosis. The immature stage is aquatic and the adult stage is very brief. Nymphs are adapted to diverse aquatic environments (needham 1935). Unlike the adults, their antennae are long and their mouthparts are functioning. The nymph can live anywhere from 3-4 weeks or up to 2.5 years before it transforms into a subimago. The presence of the subimago and the fact that mayflies "hold their wings pointing straight up" all of the time, both being only characteristic of mayflies, make this order of insects unique. -- (Earthlife World of Insects)

  1. Antennae short and bristle-like
  2. Four to nine pairs of leaf-like or fan-like gills along the sides of the abdomen
  3. Three long filaments at rear of abdomen
  1. Antennae short and bristle-like
  2. Front legs long and often held out in front of body
  3. Compound eyes large, usually covering most of the head
  4. Wings: four membranous wings with many veins and crossveins
    • front wings large, triangular
    • hind wings smaller, fan-shaped
  5. Abdomen slender, bearing two (or sometimes three) long terminal filaments
This information is from N.C. State University's Entomology Dept.


Taxonomic Category Scientific Name Common Name
Phylum Arthropoda Arthropods
Class Insecta Insects
Order Ephemeroptera Mayflies


mass swarming picture
Photo copyright Photos by Istvan Turcsanyi, L. Kossuth University, Debrecen, Hungary
[Species:Heptagenia sulphurea imago]
Photo copyright by Peter Maihofer, Gmund.
Mayfly nymph
Photo copyright by Peter Maihofer, Gmund.

Geographic distribution
Mayflies are found in freshwater habitats of all of North America as well as worldwide (Needham 1935). There are 2000 species, 200 genera, and 19 families of mayflies (Elliott and Humpesch 1983).
North America Worldwide
Number of Families 17 19
Number of Species 611 2000
This table is from N.C. State University's Entomology Dept.

Natural history
Life History & Ecology:
  • A nymph is a larva that lives in sheltered vegetation where fish can not find them (Needham 1935). They cannot fully defend themselves, and fall prey to many fish, salamanders, and dragonflies the closer they come to molting. To emerge from the last larval stage, the mayfly needs to come to the surface of the water. Larvae become more active. Emergence takes place very rapidly--from a few seconds to a minute. The subimago that emerges flies away and finds a shelter where it molts. This first adult stage lasts about 24 hours but depends upon the species. It has a dull appearance until it molts again into the imagos which is smooth and shining (Elliott and Humpesch 1983). The mayfly is inactive for most of it's adult life. The adult's legs are weak, so it does not run, walk, or crawl. The stomach stops being used for digestion in the transition, so the imagos does not eat. It simply rests until it is sexually ready to reproduce. Also in the transition is a reduction of mouthparts and antennae, an increase in eye side, and a loss of jaw muscles. These changes are made in order to mate (Needham 1935). Males form swarms that rise and fall to bring the sexes together. Females fly into the swarm to mate. Mating occurs almost immediately and usually in flight. The male mounts the female from beneath with the help of his large eyes and long forelegs. Copulation occurs while they descend and is completed before they land (Elliott and Humpesch 1983). Most females fly upstream before laying eggs. They dance over the water and fly down to deposit their eggs. The adhesive eggs come into contact with the water then stick to pebbles and stones, easily withstanding the rapidly running water. In one ovoviviparous species, the female rests for 10-14 days after copulation then lays eggs on the water surface. The eggs hatch and larvae swim away with water contact. The hatched eggs then become nymphs which starts the cycle again (Needham 1935).
Economic Importance:
  • Mayflies feed the fish that humans find valuable. The adults and imitations of adults are also used in fishing (Elliott and Humpesch 1983).
  • Interesting Facts
    • A few species of mayflies reproduce parthenogenically -- no males have ever been found (Elliott and Humpesch 1983).
    • Mayflies have the briefest existance known in the winged state among insects
    • The largest have a wing span of almost 2.5 inches (Protereisma).
    • The smallest are about 1/12 of an inch long.
    • The longest are 1 inch and the males have a tail twice as long.
    • One genera is known to be carniverous (Ameletopsis).
    • Molting of fuly winged insects occur only in this order.
    • Both sexes swarm together in Caenidae.
    • The nymph fills its stomach with water before its transition to an adult. This is later replaced by air (Needham 1935).

How to encounter
Adults can be collected with an insect net by beating bushes and trees. One can also sweep lower areas near rivers, lakes, and streams (Elliott and Humpesch 1983).

Links to other sites

  • Elliott, J. M. and U. H. Humpesch. A Key to the Adults of the British Ephemeroptera. Freshwater Biological Association; Cumbria. 1983.
  • Needham, James G., et al. The Biology of Mayflies. Comstock Publishing Company, Inc.; New York. 1935.

This page was written by Sharmeen Hossain, Ecology major. Thanks to Sabina Gupta, Denise Lim, and Dr. John Pickering for technical and web support in developing this page.

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