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Order Ephemeroptera


Soil & Water Conservation Society of Metro Halifax (SWCSMH)

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Updated: October 09, 2013      Freshwater Benthic Ecology and Aquatic Entomology Homepage


Linnean system of hierarchical classification

(Williams & Feltmate, 1992)


These have a fossil record that is relevant to the issue of the evolutionary origin of wings in the Insecta. Carboniferous mayflies include gigantic species with wing spans of atleast 45 cm. Modern Ephemeroptera number about 2000 species in 19 families, most of them associated with running water. The adults are less diverse in form than the nymphs.

The mayflies belong to the infraclass Paleoptera; their primitive wings cannot be folded over their backs. They are among the most primitive aquatic insects and probably arose in the Carboniferous period, 280-350 million years ago. The taxonomy of the immature stages is poorly known because the nymphs of many species have not yet been associated with adult forms.

Life History

Mayflies are hemimetabolous insects well known for their short-lived (ephemeral) adult phase, which usually lasts from two hours to three days. Mayflies are unique insects in that they have two adult stages. Both are winged, short-lived (1-2 hours to a maximum of 14 days) and do not feed. The subimago (dun) is a stage of sexual maturation in which the wings are semi-opaque and covered in minute hairs (microtrichia) with longer setae on the margins. Beneath the subimaginal cuticle the adult eyes, legs and genitalia are clearly visible. The mature adult (imago) that emerges when the subimago moults has much longer legs and cerci, and wings that are clear and bare.

In contrast to the imagos, mayfly nymphs exhibit considerable diversity in appearance although many stream species are dorso-ventrally flattened. Mayfly nymphs go through a large number of moults as they grow, with most species having 15-25 instars. Estimates for some species reach as high as 50 and variations occur within single species.

Distribution and Habitat

The order Ephemeroptera has a cosmopolitan distribution but is absent from the Arctic and antartic. They are absent from oceanic islands, but New Zealand has a good fauna. Chemical tolerance is less well known for mayflies than for some other groups. Life forms of mayfly larvae are diverse, but they fall into four broad categories: burrowing, flattened, swimming, and creeping.

They reach peak abundance in cool, clean headwater streams, where they are an important source of food for fish. Some species can regulate respiratory movements of gills in response to changing oxygen concentrations. Mayfly nymphs are characteristic of shallow streams and littoral areas of lakes, and are distributed widely. However, many species are restricted to specific substrata of macrophytes, sediments of waveswept or moving stream areas, or sediments of specific sized particles.

Typical nymphal habitats (Williams & Feltmate, 1992)

FamilyPrimary distributionHabitat
Suborder Schistonota
Superfamily Baetoidea/Heptagenioidea
   Siphlonuridaelargely Holarcticchiefly running water
   ColorburiscidaeS. Hemispherestony upland streams
   OniscigastridaeS. Hemispherelotic & lentic
   AmeletopsidaeS. Hemispherestony upland streams
   AmetropodidaeHolarcticlarge rivers
   Baetidaewidespreadchiefly running water
   MetretopodidaeHolarcticfast-flowing water
   Oligoneuriidaeesp. Afrotr/Neotrop/
some Holarc. & Orient.
running water
   Heptageniidaelargely Holarcticlotic & lentic-erosional
Superfamily Leptophlebioidea
   Leptophlebiidaeesp. S. Hemisphere/
some Holarc. & Orient
esp. fast-flowing waters
Superfamily Ephemeroidea
   BehningiidaeHolarcticburrowers in river sand
   Potamanthidaelargely Asian/some N.A.lotic-depositional
   Euthyplociidaeesp. Neotrop./Afrotr.sand burrowers
   Polymitarcyidaeesp. Neotrop./Afrotr./
some in Holarctic
burrowers in stream & river beds
   EphemeridaeOriental/Afrotr/Holarc.lotic & lentic burrowers
   PalingeniidaeAfrotr/Orient/Palaearc.burrowers in river beds
Suborder Pannota
Superfamily Ephemerelloidea
   Ephemerellidaewidespreadchiefly running water
   Tricorythidaeesp. Afrotr./Neotrop.lotic-deposit/lentic littoral
   Leptohyphidaeesp. Neotrop./some N.A.lotic
Superfamily Caenoidea
   NeoephemeridaeHolarctic & Orientallotic-depositional
Superfamily Prosopistomatoidea
   Baetiscidaeesp. eastern N. Amer.lotic-depositional
   ProsopistomatidaeAfrotr./some Orientallotic-depositional


They are primarily grazers and collector-gatherers. Some species are predaceous, and others have interesting adaptations for filter feeding (Oligoneuriidae). The diet of most mayflies is composed of algae and detritus.

Indicator value

These insects of inland waters are aquatic only in their juvenile stages. In general, mayfly nymphs tend to live mostly in unpolluted lakes, ponds, streams and rivers where, with densities of up to 10,000/sq.metre, they contribute substantially to secondary production. However, very small amounts of organic pollution can sometimes, initially, increase the numbers and production of certain species while others are exterminated. Species of Baetis (Family Baetidae) seem the most tolerant to pollution and these and others are often used as indicators of water quality.

Burrowing nymphs such as Hexagenia bilineata (Family Ephemeridae) do particularly well in silted impoundments and the problems associated with their mass emergence from the Mississippi River are notorious- e.g. accumulation of adult bodies on road bridges create slippery surfaces for motorists.

Physiological and ecological tolerances and requirements of common mayfly nymphs

(Mackie, 2001)

SpeciesGeneral habitatFeedingpHOxygen %Trophic
Baetis vagansgravel, streamsscraper≥7100Oligo
Epeorus vitreusgravel, streamsshredder>7100Oligo
Ephemera simulanssand, gravel, lakes, streamspredator, gatherer, shredder≥750-100Meso-Oligo
Ephemerella subvariagravel, streamsscraperapprox. 7100Oligo
Ephemerella cornutagravel, streamsscraperapprox. 7100Oligo
Heptagenia flavescenswood, rock, streamsshredder, gatherer?50-100Meso-Eutro
Hexagenia limbatamud, lakespredator>7≅100Meso-Oligo
Hexagenia recurvatamud, cold streamspredator≥7100Oligo
Isonychia bicolorswimmer, streamsfilter feeder≥7100Oligo
Paraleptophlebia debilisgravel, rocks, streamsgatherer, shredder>7100Dyst-Oligo
Rhithrogena undulatagravel, rocks, streamsgatherer≥7100Oligo
Stenacron interpunctatumrocks, lakes, streams, pondsgatherer, scraper<7 - >725-100all levels
Stenonema tripunctatumrocks, streamsgatherer, scraper≥7 - >750-100all levels
Stenonema femoratumrocks, streamsgatherer, scraper>7100Oligo
Tricorythodes minutusindifferent, streams onlygatherer>725-100Meso, Dyst

References and web URLs:

Freshwater Benthic Ecology and Aquatic Entomology Homepage                     Soil & Water Conservation Society of Metro Halifax (SWCSMH) Master Homepage

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