Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are belonging to the order Ephemeroptera. This order is part of an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies. Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families.
Mayflies have ancestral traits that were probably present in the first flying insects, such as long tails and Insect wing that do not fold flat over the abdomen. Their immature stages are aquatic fresh water forms (called "naiads" or "nymphs"), whose presence indicates a clean, unpolluted and highly oxygenated aquatic environment. They are unique among insect orders in having a fully winged terrestrial preadult stage, the subimago, which moulting into a sexually mature adult, the imago.
Mayflies "hatch" (emerge as adults) from spring to autumn, not necessarily in May, in enormous numbers. Some hatches attract tourists. Fly fishermen make use of mayfly hatches by choosing artificial fly that resemble them. One of the most famous English mayflies is Rhithrogena germanica, the fisherman's "March brown mayfly".
The brief lives of mayfly adults have been noted by naturalists and encyclopaedists since Aristotle and Pliny the Elder in classical antiquity. The German engraver Albrecht Dürer included a mayfly in his 1495 engraving The Holy Family with the Mayfly to suggest a link between heaven and earth. The English poet George Crabbe compared the brief life of a daily newspaper with that of a mayfly in the satirical poem "The Newspaper" (1785), both being known as "ephemera".
The thorax consists of three segments – the hindmost two, the mesothorax and metathorax, being fused. Each segment bears a pair of legs which usually terminate in a single claw. The legs are robust and often clad in bristles, hairs or spines. Wing pads develop on the mesothorax, and in some species, hindwing pads develop on the metathorax.
The abdomen consists of ten segments, some of which may be obscured by a large pair of operculate gills, a thoracic shield (expanded part of the prothorax) or the developing wing pads. In most taxa up to seven pairs of arise from the top or sides of the abdomen, but in some species they are under the abdomen, and in a very few species the gills are instead located on the arthropod leg of the legs, or the bases of the maxillae. The abdomen terminates in slender thread-like projections, consisting of a pair of Cercus, with or without a third central caudal filament.
Often, all the individuals in a population mature at once (a hatch), and for a day or two in the spring or autumn, mayflies are extremely abundant, dancing around each other in large groups, or resting on every available surface. In many species the emergence is synchronised with dawn or dusk, and light intensity seems to be an important cue for emergence, but other factors may also be involved. Baetis intercalaris, for example, usually emerges just after sunset in July and August, but in one year, a large hatch was observed at midday in June. The soft-bodied subimagos are very attractive to predators. Synchronous emergence is probably an adaptive strategy that reduces the individual's risk of being eaten. The lifespan of an adult mayfly is very short, varying with the species. The primary function of the adult is reproduction; adults do not feed and have only vestigial mouthparts, while their digestive systems are filled with air. Dolania americana has the shortest adult lifespan of any mayfly: the adult females of the species live for less than five minutes.
Male adults may patrol individually, but most congregate in swarms a few metres above water with clear open sky above it, and perform a nuptial or courtship dance. Each insect has a characteristic up-and-down pattern of movement; strong wingbeats propel it upwards and forwards with the tail sloping down; when it stops moving its wings, it falls passively with the abdomen tilted upwards. Females fly into these swarms, and mating takes place in the air. A rising male clasps the thorax of a female from below using his front legs bent upwards, and inseminates her. Copulation may last just a few seconds, but occasionally a pair remains in tandem and flutters to the ground. Males may spend the night in vegetation and return to their dance the following day. Although they do not feed, some briefly touch the surface to drink a little water before flying off.
Females typically lay between four hundred and three thousand eggs. The eggs are often dropped onto the surface of the water; sometimes the female deposits them by dipping the tip of her abdomen into the water during flight, releasing a small batch of eggs each time, or deposits them in bulk while standing next to the water. In a few species, the female submerges and places the eggs among plants or in crevices underwater, but in general, they sink to the bottom. The incubation time is variable, depending at least in part on temperature, and may be anything from a few days to nearly a year. Eggs can go into a quiet dormant phase or diapause. The growth rate is also temperature-dependent, as is the number of ecdysis. At anywhere between ten and fifty, these post-embryonic moults are more numerous in mayflies than in most other insect orders. The nymphal stage of mayflies may last from several months to several years, depending on species and environmental conditions.
Around half of all mayfly species whose reproductive biology has been described are parthenogenetic (able to asexually reproduce), including both partially and exclusively parthenogenetic populations and species.
Many species breed in moving water, where there is a tendency for the eggs and nymphs to get washed downstream. To counteract this, females may fly upriver before depositing their eggs. For example, the female Tisza mayfly, the largest European species with a length of , flies up to upstream before depositing eggs on the water surface. These sink to the bottom and hatch after 45 days, the nymphs their way into the sediment where they spend two or three years before hatching into subimagos.
When ready to emerge, several different strategies are used. In some species, the transformation of the nymph occurs underwater and the subimago swims to the surface and launches itself into the air. In other species, the nymph rises to the surface, bursts out of its skin, remains quiescent for a minute or two resting on the (cast skin) and then flies upwards, and in some, the nymph climbs out of the water before transforming.
In most species, the nymphs are or , feeding on algae, or detritus, but in a few species, they are predators of chironomid and other small insect larvae and nymphs. Nymphs of Povilla burrow into submerged wood and can be a problem for boat owners in Asia. Some are able to shift from one feeding group to another as they grow, thus enabling them to utilise a variety of food resources. They process a great quantity of organic matter as nymphs and transfer a lot of phosphates and nitrates to terrestrial environments when they emerge from the water, thus helping to remove pollutants from aqueous systems. Along with caddisfly larvae and gastropoda, the grazing of mayfly nymphs has a significant impact on the primary producers, the plants and algae, on the bed of streams and rivers.
The nymphs are eaten by a wide range of predators and form an important part of the aquatic food chain. Fish are among the main predators, picking nymphs off the bottom or ingesting them in the water column, and feeding on emerging nymphs and adults on the water surface. Carnivorous stonefly, caddisfly, alderfly and dragonfly larvae feed on bottom-dwelling mayfly nymphs, as do aquatic beetles, leeches, crayfish and . Besides the direct mortality caused by these predators, the behaviour of their potential prey is also affected, with the nymphs' growth rate being slowed by the need to hide rather than feed. The nymphs are highly susceptible to Water pollution and can be useful in the biomonitoring of water bodies. Once they have emerged, large numbers are preyed on by birds, bats and by other insects, such as Rhamphomyia longicauda.
Mayfly nymphs may serve as hosts for such as and trematodes. Some of these affect the nymphs' behaviour in such a way that they become more likely to be predated. Other nematodes turn adult male mayflies into quasi-females which haunt the edges of streams, enabling the parasites to break their way out into the aqueous environment they need to complete their life cycles. The nymphs can also serve as intermediate hosts for the horsehair worm Paragordius varius, which causes its definitive host, a grasshopper, to jump into water and drown.
The threat to mayflies applies also to their eggs. "Modest levels" of pollution in rivers in England are sufficient to kill 80% of mayfly eggs, which are as vulnerable to pollutants as other life-cycle stages; numbers of the blue-winged olive mayfly ( Baetis) have fallen dramatically, almost to none in some rivers. The major pollutants thought to be responsible are fine sediment and phosphate from agriculture and sewage.
The status of many species of mayflies is unknown because they are known from only the original collection data. Four North American species are believed to be extinct. Among these, 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 is known from a single specimen, collected from the "foothills of Colorado" in 1873, but despite intensive surveys of the Colorado mayflies reported in 1984, it has not been rediscovered.
The International Union for Conservation of Nature (IUCN) red list of threatened species includes one mayfly: Tasmanophlebia lacuscoerulei, the large blue lake mayfly, which is a native of Australia and is listed as endangered because its alpine habitat is vulnerable to climate change.
As of 2012, over 3,000 species of mayfly in 42 families and over 400 genera are known worldwide, including about 630 species in North America. Mayflies are an ancient group of winged (pterygote) insects. Putative fossil stem group representatives (e.g. Syntonopteroidea-like Lithoneura lameerrei) are already known from the late Carboniferous. The name Ephemeroptera is from the Ancient Greek ἐφήμερος, ephemeros "short-lived" (literally "lasting a day", cf. English "ephemeral"), and πτερόν, pteron, "insect wing", referring to the brief lifespan of adults. The English common name is for the insect's emergence in or around the month of May in the UK. The name shadfly is from the Atlantic fish the shad, which runs up American East Coast rivers at the same time as many mayflies emerge.
From the Permian, numerous stem group representatives of mayflies are known, which are often lumped into a separate taxon Permoplectoptera (e.g. including Protereisma permianum in the Protereismatidae, and Misthodotidae). The larvae of Permoplectoptera still had 9 pairs of abdominal gills, and the adults still had long hindwings. Maybe the fossil family Cretereismatidae from the Lower Cretaceous Crato Formation of Brazil also belongs as the last offshoot to Permoplectoptera. The Crato outcrops otherwise yielded fossil specimens of modern mayfly families or the extinct (but modern) family Hexagenitidae. However, from the same locality the strange larvae and adults of the extinct family Mickoleitiidae (order Coxoplectoptera) have been described, which represents the fossil sister group of modern mayflies, even though they had very peculiar adaptations such as raptorial forelegs.
The oldest mayfly inclusion in amber is Cretoneta zherichini (Leptophlebiidae) from the Lower Cretaceous of Siberia. In the much younger Baltic amber numerous inclusions of several modern families of mayflies have been found (Ephemeridae, Potamanthidae, Leptophlebiidae, Ametropodidae, Siphlonuridae, Isonychiidae, Heptageniidae, and Ephemerellidae). The modern genus Neoephemera is represented in the fossil record by the Ypresian species N. antiqua from Washington state.
Grimaldi and Engel, reviewing the phylogeny in 2005, commented that many cladistic studies had been made with no stability in Ephemeroptera suborders and infraorders; the traditional division into Schistonota and Pannota was wrong because Pannota is derived from the Schistonota.
The phylogeny of the Ephemeroptera was first studied using molecular analysis by Ogden and Whiting in 2005. They recovered the Baetidae as sister to the other clades.
Mayfly phylogeny was further studied using morphological and molecular analyses by Ogden and others in 2009. They found that the Asian genus Siphluriscus was sister to all other mayflies. Some existing lineages such as Ephemeroidea, and families such as Ameletopsidae, were found not to be monophyletic, through convergence among nymphal features.
The following traditional classification, with two suborders Pannota and Schistonota, was introduced in 1979 by W. P. McCafferty and George F. Edmunds. The list is based on Peters and Campbell (1991), in Insects of Australia.
Suborder Pannota
Suborder Schistonota
In 1495 Albrecht Dürer included a mayfly in his engraving The Holy Family with the Mayfly. The critics Larry Silver and Pamela H. Smith argue that the image provides "an explicit link between heaven and earth ... to suggest a cosmic resonance between sacred and profane, celestial and terrestrial, macrocosm and microcosm."
The Ancient Roman encyclopaedist Pliny the Elder described the mayfly as the "hemerobius" in his Natural History:
The Roman lawyer Cicero wrote philosophically of them in his Tusculan Disputations:
In his 1789 book The Natural History and Antiquities of Selborne, Gilbert White described in the entry for "June 10th, 1771" how
The mayfly has come to symbolise the transitoriness and brevity of life. The English poet George Crabbe, known to have been interested in insects, compared the brief life of a newspaper with that of mayflies, both being known as "Ephemera", things that live for a day:
The theme of brief life is echoed in the artist Douglas Florian's 1998 poem, "The Mayfly". The American Poet Laureate Richard Wilbur's 2005 poem "Mayflies" includes the lines "I saw from unseen pools a mist of flies, In their quadrillions rise, And animate a ragged patch of glow, With sudden glittering".
Another literary reference to mayflies is seen in The Epic of Gilgamesh, one of the earliest surviving great works of literature. The briefness of Gilgamesh's life is compared to that of the adult mayfly. In Szeged, Hungary, mayflies are celebrated in a monument near the Belvárosi bridge, the work of local sculptor Pal Farkas, depicting the courtship dance of mayflies. The American playwright David Ives wrote a short comedic play, Time Flies, in 2001, as to what two mayflies might discuss during their one day of existence.
Izaak Walton describes the use of mayflies for catching trout in his 1653 book The Compleat Angler; for example, he names the "Green-drake" for use as a natural fly, and "duns" (mayfly subimagos) as artificial flies. These include for example the "Great Dun" and the "Great Blue Dun" in February; the "Whitish Dun" in March; the "Whirling Dun" and the "Yellow Dun" in April; the "Green-drake", the "Little Yellow May-Fly" and the "Grey-Drake" in May; and the "Black-Blue Dun" in July. Nymph or "wet fly" fishing was restored to popularity on the of England by G. E. M. Skues with his 1910 book Minor Tactics of the Chalk Stream. In the book, Skues discusses the use of duns to catch trout. The March brown is "probably the most famous of all British mayflies", having been copied by angling to catch trout for over 500 years.
Some English beside trout streams such as the River Test in Hampshire are named "The Mayfly".
During the weekend of 13–14 June 2015, a large swarm of mayflies caused several vehicular accidents on the Columbia–Wrightsville Bridge, carrying Pennsylvania Route 462 across the Susquehanna River between Columbia and Wrightsville, Pennsylvania. The bridge had to be closed to traffic twice during that period due to impaired visibility and obstructions posed by piles of dead insects.
Two vessels of the Royal Navy were named : a torpedo boat launched in January 1907, and a Fly-class river gunboat constructed in sections at Yarrow in 1915.
The Seddon Mayfly, which was constructed in 1908, was an aircraft that was unsuccessful in early flight. The first aircraft designed by a woman, Lilian Bland, was titled the Bland Mayfly.
Research on genome expression in the mayfly Cloeon dipterum, has provided ideas on the evolution of the insect wing and giving support to the so-called gill theory which suggests that the ancestral insect wing may have evolved from larval gills of aquatic insects like mayflies.
Mayfly larvae do not survive in polluted aquatic habitats and, thus, have been chosen as bioindicators, markers of water quality in ecological assessments.
In marketing, Nike produced a line of running shoes in 2003 titled "Mayfly". The shoes were designed with a wing venation pattern like the mayfly and were also said to have a finite lifetime. The telecommunication company Vodafone featured mayflies in a 2006 branding campaign, telling consumers to "make the most of now".
Description
Nymph
Subimago
Imago
Biology
Reproduction and life cycle
Ecology
Effects on ecosystem functioning
Distribution
Conservation
Taxonomy and phylogeny
Phylogeny
In human culture
In art
+ Mayfly in art Mayflies drawn by Augerius Clutius in De Hemerobio, 1634
File:Jan Sadeler after Maarten de Vos Heron Mayfly Flying Fish 1587.jpg Mayfly by Jan Sadeler after Maerten de Vos, detail from The Fifth Day: The Creation of the Birds and Fishes, c. 1587
File:Albrecht Dürer - The Holy Family with the Mayfly (NGA 1943.3.3453).jpg Albrecht Dürer's engraving The Holy Family with the Mayfly, 1495
File:Insect in Dürer's Holy Family with the Mayfly detail.jpg Detail of "mayfly" in lower right corner of Albrecht Dürer's engraving The Holy Family with the Mayfly, 1495
File:Mayflies in Sunset Dance Gilbert White Natural History of Selborne.jpg "May-Flies in Sunset Dance" by Philip Henry Gosse in a Victorian edition of Gilbert White's Natural History of Selborne
In literature
In fly fishing
As a spectacle
As food
As a name for ships and aircraft
Other human uses
Notes
External links
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