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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.
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.
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.
Family | Primary distribution | Habitat |
---|---|---|
Suborder Schistonota | ||
Superfamily Baetoidea/Heptagenioidea | ||
Siphlonuridae | largely Holarctic | chiefly running water |
Colorburiscidae | S. Hemisphere | stony upland streams |
Oniscigastridae | S. Hemisphere | lotic & lentic |
Ameletopsidae | S. Hemisphere | stony upland streams |
Ametropodidae | Holarctic | large rivers |
Baetidae | widespread | chiefly running water |
Metretopodidae | Holarctic | fast-flowing water |
Oligoneuriidae | esp. Afrotr/Neotrop/ some Holarc. & Orient. | running water |
Heptageniidae | largely Holarctic | lotic & lentic-erosional |
Superfamily Leptophlebioidea | ||
Leptophlebiidae | esp. S. Hemisphere/ some Holarc. & Orient | esp. fast-flowing waters |
Superfamily Ephemeroidea | ||
Behningiidae | Holarctic | burrowers in river sand |
Potamanthidae | largely Asian/some N.A. | lotic-depositional |
Euthyplociidae | esp. Neotrop./Afrotr. | sand burrowers |
Polymitarcyidae | esp. Neotrop./Afrotr./ some in Holarctic | burrowers in stream & river beds |
Ephemeridae | Oriental/Afrotr/Holarc. | lotic & lentic burrowers |
Palingeniidae | Afrotr/Orient/Palaearc. | burrowers in river beds |
Suborder Pannota | ||
Superfamily Ephemerelloidea | ||
Ephemerellidae | widespread | chiefly running water |
Tricorythidae | esp. Afrotr./Neotrop. | lotic-deposit/lentic littoral |
Leptohyphidae | esp. Neotrop./some N.A. | lotic |
Superfamily Caenoidea | ||
Neoephemeridae | Holarctic & Oriental | lotic-depositional |
Caenidae | widespread | lotic-deposit/lentic-litt. |
Superfamily Prosopistomatoidea | ||
Baetiscidae | esp. eastern N. Amer. | lotic-depositional |
Prosopistomatidae | Afrotr./some Oriental | lotic-depositional |
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.
Species | General habitat | Feeding | pH | Oxygen % | Trophic level |
---|---|---|---|---|---|
Baetis vagans | gravel, streams | scraper | ≥7 | 100 | Oligo |
Epeorus vitreus | gravel, streams | shredder | >7 | 100 | Oligo |
Ephemera simulans | sand, gravel, lakes, streams | predator, gatherer, shredder | ≥7 | 50-100 | Meso-Oligo |
Ephemerella subvaria | gravel, streams | scraper | approx. 7 | 100 | Oligo |
Ephemerella cornuta | gravel, streams | scraper | approx. 7 | 100 | Oligo |
Heptagenia flavescens | wood, rock, streams | shredder, gatherer | ? | 50-100 | Meso-Eutro |
Hexagenia limbata | mud, lakes | predator | >7 | ≅100 | Meso-Oligo |
Hexagenia recurvata | mud, cold streams | predator | ≥7 | 100 | Oligo |
Isonychia bicolor | swimmer, streams | filter feeder | ≥7 | 100 | Oligo |
Paraleptophlebia debilis | gravel, rocks, streams | gatherer, shredder | >7 | 100 | Dyst-Oligo |
Rhithrogena undulata | gravel, rocks, streams | gatherer | ≥7 | 100 | Oligo |
Stenacron interpunctatum | rocks, lakes, streams, ponds | gatherer, scraper | <7 - >7 | 25-100 | all levels |
Stenonema tripunctatum | rocks, streams | gatherer, scraper | ≥7 - >7 | 50-100 | all levels |
Stenonema femoratum | rocks, streams | gatherer, scraper | >7 | 100 | Oligo |
Tricorythodes minutus | indifferent, streams only | gatherer | >7 | 25-100 | Meso, Dyst |
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