Minnesota Mayflies

Order Ephemeroptera

Ephemeroptera is the order of small to medium-sized flying insects known as mayflies. They have elongated, very soft bodies. The forewings are triangular, very large, and have many veins. They are held together above the body when at rest. The hindwings are small and round, or in some species missing. The abdomen has 2 or 3 hair-like tails. The antennae are short, bristle-like, and inconspicuous. The last part of the leg (tarsus), corresponding to the foot, has 3 or 5 segments. The mouthparts are small, poorly developed, and non-functional. Adults often emerge in large numbers, sometimes piling up on the shore. Many species engage in swarming flights, where they fly up and down in unison. They do not feed and seldom live more than 1 or 2 days.

The young, called nymphs, are aquatic. They have leaf-like gills along the sides of the abdomen, and 3 hair-like tails at the end of the abdomen. Most mayfly nymphs develop in streams and rivers, some develop in lakes and ponds. The feed on small aquatic organisms and organic debris. They swim to the water surface or crawl onto emergent vegetation or rocks to complete the second-to-last molt. This subadult stage has functional wings and is called a subimago. They fly to nearby vegetation and molt one last time, emerging as adults. Mayflies are unique as the only insect that molts again after developing functional wings.

Mayflies are an important food source for freshwater fish. Fly fisherpersons use mayflies as bait.

There are more than 3,000 species in more than 400 genera in 42 families of mayflies worldwide. There are 611 species in 59 genera in 21 families in North America north of Mexico. There are estimated to be 100 to 119 species in Minnesota.


pond olive

Photo by Alfredo Colon


Recent Additions

Pond olive


Pond olive (Cloeon dipterum) is a small minnow mayfly. It occurs throughout Europe, where it is native, and in Asia and North America, where it has been introduced. The earliest North American record is from Illinois in 1953. It is now widespread across the continent. In the United States it is currently mostly restricted to the northeast and to Washington state. It is rare in Minnesota. Nymphs are found mostly in ponds, but also in the shallow margins of lakes and in slow areas of rivers and streams. They feed on algae, small aquatic organisms, and organic debris. Adults are found on vegetation near ponds. They do not feed and seldom live more than 1 or 2 days.

Adults are reddish-brown and have 2 very long hair-like tails at the end of the abdomen. The compound eyes on the female are on the sides of the head. On the male the compound eyes have additional large, orange, turban-like parts that meet at the top of the head. These adaptations are said to allow the male to isolate in a swarm females that are not yet paired with another male. Some authors say that pond olives have no hindwings. Carl Linnaeus in 1761 described the hindwings as “hardly present.”

  pond olive  
    Photo by Alfredo Colon  
Other Recent Additions







This list includes only mayflies that have been recorded in Minnesota, but not all of the mayflies found in Minnesota.

Profile Photo Video        



























pond olive


Aphrodite’s flat-headed mayfly (Leucrocuta aphrodite)


brown drake (Ephemera simulans)


brush-legged mayfly (Isonychia velma)


cloudy prong-gilled mayfly (Leptophlebia nebulosa)


common spiny-headed burrowing mayfly (Pentagenia vittigera)


dark cahill (Stenonema femoratum)


early brown spinner (Leptophlebia cupida)


emergent mayfly (Hexagenia bilineata)


fragile prong-gilled mayfly (Paraleptophlebia debilis)


giant mayfly (Hexagenia limbata)


golden drake (Anthopotamus distinctus)


Hebe’s flat-headed mayfly (Leucrocuta hebe)


lake hex (Hexagenia atrocaudata)


Laurentian armored mayfly (Baetisca laurentina)


mahogany dun (Isonychia bicolor)


march flat-headed mayfly (Maccaffertium vicarium)


modest flat-headed mayfly (Maccaffertium modestum)


northern summer mayfly (Siphlonurus alternatus)


orange cahill (Stenacron interpunctatum)

Profile Photo Video   pond olive (Cloeon dipterum)  

pretty small minnow mayfly (Callibaetis pretiosus)


red speckled dun (Callibaetis ferrugineus ferrugineus)


southern flat-headed mayfly (Maccaffertium mexicanum)


stream mayfly (Nixe kennedyi)


terminal flat-headed mayfly (Maccaffertium terminatum)


Walker’s tusked sprawler (Anthopotamus verticis)


white fly (Ephoron leukon)




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Created 11/5/2020

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