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For Insects, Spiders & Their Kin
For the United States & Canada
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Order Ephemeroptera - Mayflies

Baetidae, genus Baetis - Baetis Hexagenia limbata mayfly - Isonychia Mayfly - Leptophlebia cupida Flatheaded Mayfly - Stenonema femoratum - female Mayfly near valley stream - Baetis tricaudatus Mayfly - Maccaffertium modestum Mayfly July 8 - Procloeon nelsoni - male
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Ephemeroptera (Mayflies)
Other Common Names
in angling/flyfishing, an adult mayfly (imago) is called a spinner; the winged pre-adult (subimago) is called a dun; and many species have common names(1)
Synonyms and other taxonomic changes
The classification/nomenclature in the Guide generally follows (2)
Explanation of Names
Ephemeroptera Hyatt & Arms 1891
Greek ephemeros 'of/for a day' + pteron 'wing' -- refers to the short-lived adults
MAYFLY: adults appear in numbers in May
~650 spp. in ~110 genera of 23 families in our area(2); worldwide, ~3350 spp. in >440 genera of at least 42 families(3)(4)(5); 300 spp. in se. US(6), 204 in the Carolinas(7)(8), 71 in FL(9)
Overview of our fauna * taxa not yet in the guide(10)
Order Ephemeroptera


Infraorder PANNOTA
Superfamily Caenoidea
Superfamily Ephemerelloidea

Superfamily Ephemeroidea
Superfamily *Euthyplocioidea
Superfamily Potamanthoidea
Superfamily Heptagenioidea
1‒30 mm
Adult (imago): delicate insects; thorax and abdomen bare, often shiny; front legs often held forward and sometimes upward at rest; hindwings much smaller than forewings (may be absent)
Subimago: wings cloudy, body dull and pubescent, with appendages somewhat shorter ‒otherwise similar to imago
Nymph (usually called larva): antennae short; abdomen with lateral gills and 2‒3 long tail filaments
keys: NA, genera, larvae & adults(11); ne. NA, genera, nymphs(12)
local guides/keys(13)(14)(15)(16)(17)(18)(19)(20)(21)
worldwide and throughout NA; for ranges of nearctic spp., see(22)(2)(23)
some emerge in late April (earlier in the south) but the greatest numbers first appear in May
nymphs feed on organic matter such as plant material or algae and debris that accumulates on rocks or other substrates in flowing water (predation recorded in some); adults do not feed
Life Cycle
Adult males usually gather in mid-air swarms 5‒15 m above the ground; females fly into the swarm, and mating occurs in flight. Females drop their eggs while flying low over the water, or by dipping the abdomen; some go underwater to lay eggs.
Mayflies are the only insects that molt in winged condition. There may be from several to dozens nymphal instars. Mature nymphs swim to water surface or crawl onto rocks or plants, then molt into winged subimagoes which then molt again into adults (imagoes). Adult lifespan ranges from 1.5 hours to two weeks, most adults live 48‒72 hrs.
Adults and nymphs are an important source of food for fish and other aquatic wildlife. Anglers often use mayflies as bait.
See Also
stonefly and caddisfly adults hold their wings together horizontally over the abdomen, and hugged closed to the body
stonefly nymphs have filamentous gills (not plate-like), and have just two cerci (never the median filament)
Print References
Internet References
Works Cited
1.Neuswanger J. (2004-2014) Aquatic insects of American trout streams
2.Mayfly Central
3.Ephemeroptera of the World
4.Barber-James H., Sartori M., Gattolliat J-L., Webb J. (2013) World checklist of freshwater Ephemeroptera species
5.Global diversity of mayflies (Ephemeroptera, Insecta) in freshwater
Barber-James, H.M., Gattolliat, J.L., Sartori, M. & Hubbard, M.D. 2008. Hydrobiologia, 595: 339–350.
6.The mayflies (Ephemeroptera) of the southeastern United States
Mccafferty W.P., Lenat D.R., Jacobus L.M., Meyer M.D. 2010. Trans. Am. Ent. Soc. 136: 221-233.
7.Mayflies (Ephemeroptera) of North Carolina and South Carolina: An update
M.L. Pescador, D.R. Lenat, M.D. Hubbard. 1999. Florida Entomologist 82(2): 316-332.
8.The Ephemeroptera of North Carolina: A biologist’s handbook with standard taxonomic effort levels. Version 3.3
S.R. Beaty. 2011. North Carolina Department of Environment and Natural Resources. 48 + 9 pp.
9.The Mayflies of Florida: Revised edition
Berner L., Pescador M.L. 1988. University Presses of Florida. 431 pp.
10.Aquatic Orders Wish List
11.Aquatic Insects of North America
R. W. Merritt, K. W. Cummins, M.B. Berg. 2008. Kendall/Hunt.
12.Freshwater macroinvertebrates of Northeastern North America
Peckarsky, B. L., P. Fraissinet, M. A. Penton, and D. J. Conklin, Jr. 1990. Cornell University Press, Ithaca, NY.
13.Bright E. (2002-2011) Aquatic Insects of Michigan
14.Clifford H.F. (1991) Aquatic invertebrates of Alberta
15.Ziser S.W. (2008-2012) The aquatic invertebrates of Texas
16.Digital key to aquatic insects of North Dakota
17.Hadden J. (2010) Upper Delaware River insect identification - Photos and Biology of Aquatic Insects - Mayfly Section
19.Aquatic Insects of California
Robert L. Usinger, Editor. 1956. University of California Press.
20.Guide to aquatic macroinvertebrates of the Upper Midwest
Bouchard R.W., Jr. 2004. Water Resources Center, U. of Minnesota, St. Paul, MN. 208 pp.
21.Guide to the mayfly (Ephemeroptera) nymphs of Florida
Pescador M.L., Richard B.A. 2004. Dept Envir. Prot., Div. Water Resource Management, Tallahassee. 168 pp.
22.Rohrbeck R. (2004-2014) Flyfishing entomology
23.Kondratieff B.C., ed. (2000-) Mayflies of the United States
24.Ephemeroptera of South America (Aquatic Biodiversity of Latin America Series, Vol. 2.)
Dominguez E., Molineri C., Pescador M.L., Hubbard M.D., Nieto C. 2006. Pensoft Publishers. 646 pp.
25.The mayflies of Europe (Ephemeroptera)
Bauernfeind E., Soldán T. 2012. Brill Academic Publishers. 781 pp.
26.Ephemeroptera Galactica, the ephemeropterists' home page