Suborder Schistonota
Superfamily Baetoidea
Siphlonuridae
Baetidae
Oniscigastridae
Ameletopsidae
Ametropodidae
Superfamily Heptagenioidea
Coloburiscidae
Oligoneuriidae
Isonychiidae
Heptageniidae
Superfamily Leptophlebioidea
Leptophlebiidae
Superfamily Ephemeroidea
Behningiidae
Potamanthidae
Euthyplociidae
Polymitarcydae
Ephemeridae
Palingeniidae
Suborder Pannota
Superfamily Ephemerelloidea
Ephemerellidae
Leptohyphidae
Tricorythidae
Superfamily Caenoidea
Neoephemeridae
Baetiscidae
Caenidae
Prosopistomatidae
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", "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 good quality, perhaps even good enough to drink without distilling or boiling.