Harvard University's Caribbean Insects: Thysanura

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The Ephemeroptera, also known as the mayflies, is a primitive insect order. Mayflies spend the vast majority of their life as aquatic nymphs, and most spend only a few days as adults. In fact, the mayfly holds the record for the shortest reproductive lifespan – a female who lives only 5 minutes, during which time she must mate and lay eggs. Mayflies are unique in having two winged stages, the subimago and the imago (reproductive adult). One reason the adult stage is so short-lived is that adults have only vestigial mouthparts and thus cannot feed. In some groups, the legs (except the male’s forelegs that he uses to grab the female during mating) are also absent in adults.

Many species have more or less synchronous adult stages, which can result in huge, short-lived swarms of mayflies. Once their adult stage is finished, the dead mayflies can cause road blockage and traffic accidents because they are so numerous and thick on the ground.

Approximately 2500 species worldwide. 675 species in 21 families reported from North America. 100 species in 39 genera from 9 families reported from Central America. 127 species in 35 genera reported from the Neotropics (older estimate: Needham and Murphy, 1924). 20 species in 6 genera reported from Puerto Rico (older estimate: Traver, 1938).

Economic Importance:
The presence of mayflies is sometimes used as an indicator of environmental quality and water purity. Nymphs can be very abundant, and they probably are an important food for freshwater fish. Mayflies, both imagos and subimagos, are used as bait by fly fishers. During mass emergences, mayfly carcasses can block roads. Occasionally they are salvaged and used as fertilizer, bird food, or fish bait.

Recognizing Mayflies:
Mayflies have characteristic membranous, triangular forewings. They typically have four wings, but the smaller, more rounded hindwings have been lost in some groups. Adults have three or two long, slender "tails" that protrude from the end of the abdomen. The front legs are usually much longer than the remaining legs (if present). Males have paired penes, and females have paired genital openings.

Collection and Preservation Methods:
Adult stages are very short-lived, and thus they must be collected within a short window of time. They can be caught with a long-handled net. However, they often fly swarm quite high in the air. Adults may be attracted to lights at night. Malaise traps are also a good place to catch adult mayflies. Recall that subimagos are also winged. They can be distinguished by their dull coloration and pubescence. If captured, they should be reared until they molt (usually a very short time) in a small cardboard box with a transparent window.

Adults are extremely fragile. They may be pinned, pointed, or placed in alcohol. Where coloration is important, pinning is preferable. However, pinned specimens are more likely to shrivel and break.
Nymphs can be captured using dip nets. Nymphs should be preserved in alcohol or reared to the adult stage.

Bener, L. and M. L. Pescador. 1988, The Mayflies of Florida. University Presses of Florida: Tallahassee.

Edmunds, G.F., Jr., S. L. Jensen, and L. Berner. 1976. The Mayflies of North and Central America. University of Minnesota Press, Minneapolis.

Ephemeroptera - General information from the Tree of Life project

Mayflies of Central America - Species list

Mayflies of North America - Species list

McCafferty, W. P. and C.R. Lugo-Ortiz. 1996. Los Efemeropteros (Ephemeroptera) de la America Central. Revista Nicaraguense de Entomologica.

McCafferty, W. P. 1996. The Ephemeroptera species of North American Ephemeroptera and index to their complete nomenclature. Transactions of the American Entomological Society 122: 1-54.

Needham, J.G. and H. E. Murphy. 1924. Neotropical Mayflies. Bulletin of the Lloyd Library 24: 1-79.

Taxonomic key to Ephemeroptera families

Traver, J.R. 1938. Mayflies of Puerto Rico. Journal of Agriculture of the University of Puerto Rico 22: 5-42.


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