Mayflies are aquatic insects 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.
Baetidae is a family of mayflies with about 1000 described species in 110 genera distributed worldwide. These are among the smallest of mayflies, adults rarely exceeding 10 mm in length excluding the two long slender tails and sometimes much smaller, and members of the family are often referred to as small mayflies or small minnow mayflies. Most species have long oval forewings with very few cross veins but the hindwings are usually very small or even absent. The males often have very large eyes, shaped like turrets above the head.
The Heptageniidae are a family of mayflies with over 500 described species mainly distributed in the Holarctic, Oriental, and Afrotropical regions, and also present in the Central American Tropics and extreme northern South America.
Caenis is a genus of mayflies. They are very small in size, sometimes with a body of only an 1/8 of an inch (3.2 mm).
Cloeon is a cosmopolitan genus of mayflies of the family Baetidae.
Ecdyonurus is a genus of mayflies of the family Heptageniidae.
Cinygmula is a genus of flatheaded mayflies in the family Heptageniidae. There are at least 30 described species in Cinygmula.
Epeorus is a genus of mayflies in the family Heptageniidae.
Heptagenia is a genus of flatheaded mayflies in the family Heptageniidae. There are at least 20 described species in Heptagenia.
Labiobaetis is a genus of mayflies in the family Baetidae.
Choroterpes is a genus of mayflies in the family Leptophlebiidae faound in the Americas, Europe, Africa and Asia.
Paraleptophlebia is a genus of mayflies in the family Leptophlebiidae. Commonly found in North America and parts of Western Europe including the British Isles.
Baetiscidae is a family of mayflies. It contains a single extant genus, Baetisca, native to North America with around 12 species. The family is noted for their spined armoured larvae, which live in flowing water pools and on the edges of streams where they are detritivores, consuming fine particles of organic matter. Three other extinct genera are known, extending back to the Early Cretaceous. They are closely related to Prosopistomatidae which have unusual, beetle-like nymphs as well as the extinct genus Cretomitarcys, with the three groups constituting the clade Carapacea.
Ametropodidae is a family of mayflies in the order Ephemeroptera. There are at least three genera and three described species in Ametropodidae.
Homoeoneuria is a genus of brushleg mayflies in the family Oligoneuriidae. There are at least 5 described species in Homoeoneuria.
Oligoneuriidae is a family of mayflies with a pantropical distribution. They are also known as brushlegged mayflies due to the presence of two rows of setae used for filtration on the front legs of their nymphs. Nymphs also have tufts of gills at the base of their maxillae. There are at least 68 described species in over a dozen genera.
