AskDefine | Define mayfly

Dictionary Definition

mayfly n : slender insect with delicate membranous wings having an aquatic larval stage and terrestrial adult stage usually lasting less than two days [syn: dayfly, shadfly]

User Contributed Dictionary



  1. Any of many fragile insects, of the order Ephemeroptera, that develop in fresh water, and live very briefly as adults.


Related terms

Extensive Definition

Mayflies are insects which belong to the Order Ephemeroptera (from the Greek ephemeros = "short-lived", pteron = "wing", referring to the short life span of adults). They have been placed into an ancient group of insects termed the Paleoptera, which also contains the dragonflies and damselflies. They are aquatic insects whose immature stage (called naiad or, colloquially, nymph) usually lasts one year in fresh water. The adults are short-lived, from a few hours to a few days depending on the species. About 2,500 species are known worldwide, including about 630 species in North America. Common names for mayflies include "dayfly", "shadfly", "Green Bay Flies", "Canadian soldier", and "fishfly" .
The mayfly belongs to group 1 taxa, or pollution–sensitive animals. This means if mayflies are in or around the water, the water should be of a good quality.


The naiad live primarily in streams under rocks, decaying vegetation, or in the sediment. Few species live in lakes, but they are among the most prolific. For example, the emergence of one species of Hexagenia was recorded on doppler radar along the shores of Lake Erie .
Most species feed on algae or diatoms, but there are a few predatory species. The naiad stage may last from several months to as long as several years, with a number of moults along the way. Mayfly naiads are distinctive in that most have seven pairs of gills on the dorsum of the abdomen. In addition, most possess three long cerci or tails at the end of their bodies. (Some species, notably in the genus Epeorus, have only two tails.) In the last aquatic stage, dark wingpads are visible. Developmentally, these insects are considered hemimetabolous insects. A more casual and familiar term is incomplete metamorphosis. Mayflies are unique among the winged insects in that they moult one more time after acquiring functional wings (this is also known as the alate stage); this second-to-last winged instar is usually very short, often a matter of hours, and is known as a subimago or to fly fishermen as a dun. This stage is a favourite food of many fish, and many fishing flies are modelled to resemble them.


The lifespan of an adult mayfly can vary from just 30 minutes to one day depending on the species. The primary function of the adult is reproduction; the mouthparts are vestigial, and the digestive system is filled with air. The wings are membranous (similar to a house fly's wings but with many more veins) and are held upright like those of a butterfly. The forewings are much larger than the hind wings. In most species, the males' eyes are usually large and the front legs unusually long, for use in locating and grasping females during mid-air mating. In some species, all legs aside from the males' front legs are useless.
It often happens that all the mayflies in a population mature at once (the hatch), and for a day or two in the spring or fall, mayflies will be everywhere, dancing around each other in large groups, or resting on every available surface. This happens in mid-June on the Tisza River in Serbia and Hungary; this kind of mayfly is called the tiszavirág (in Hungarian) or "tiski cvet" in Serbian which is translated as "Tisza flower". This natural phenomenon is called Tisza blooming. In certain regions of New Guinea and Africa, mayflies are eaten when they emerge en masse on a certain day.
Because of its short lifespan, the mayfly is also called one–day fly in some languages — French éphémère, German Eintagsfliege, Dutch eendagsvlieg, Slovenian enodnevnica, Swedish dagsslända.


Both immature and adult mayflies are an important part of the food web, particularly for carnivorous fish such as trout in cold water streams or bass and catfish in warm water streams. They do not feed (mouthparts are vestigial), and some species emerge, reproduce, and die in a single day. Males generally fly in swarms that undulate in the air 5-15 meters above the ground.


The status of most species of mayflies is unknown because many species are only known from the original collection data. Four North American species are believed to be extinct:-
  • Pentagenia robusta was originally collected from the Ohio River near Cincinnati, but this species has not been seen since its original collection in the 1800s.
  • Ephemera compar was reported from the "foothills of Colorado". Despite intensive surveys of the Colorado mayflies, this species has not been collected in the past 50 years.
  • The large blue lake mayfly, Tasmanophlebia lecuscoerulea, is listed as vulnerable.


Scientific literature

  • The mayflies of Florida
  • The mayflies of North and Central America
  • The biology of mayflies

Popular sources

  • Firefly Encyclopedia of Insects and Spiders
mayfly in Catalan: Efemeròpter
mayfly in Czech: Jepice
mayfly in Danish: Døgnflue
mayfly in German: Eintagsfliegen
mayfly in Estonian: Ühepäevikulised
mayfly in Modern Greek (1453-): Εφημερόπτερα
mayfly in Spanish: Ephemeroptera
mayfly in Esperanto: Efemeroj
mayfly in French: Ephemeroptera
mayfly in Korean: 하루살이목
mayfly in Ido: Efemero
mayfly in Icelandic: Dægurflugur
mayfly in Italian: Ephemeroptera
mayfly in Hebrew: בריומאים
mayfly in Georgian: ერთდღიურები
mayfly in Latin: Ephemeroptera
mayfly in Latvian: Viendienīšu kārta
mayfly in Luxembourgish: Schielmécken
mayfly in Lithuanian: Lašalai
mayfly in Dutch: Haften
mayfly in Japanese: カゲロウ
mayfly in Norwegian: Døgnfluer
mayfly in Norwegian Nynorsk: Døgnfluge
mayfly in Polish: Jętki (owady)
mayfly in Portuguese: Ephemeroptera
mayfly in Russian: Подёнки
mayfly in Slovenian: Enodnevnice
mayfly in Swedish: Dagsländor
mayfly in Ukrainian: Одноденки
mayfly in Walloon: Waermaye
mayfly in Chinese: 蜉蝣目
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