Western Iron Dun vs Flat-headed Mayfly

Side-by-side species comparison

Attribute Western Iron Dun Flat-headed Mayfly
Scientific Name Epeorus longimanus Epeorus assimilis
Order Ephemeroptera Ephemeroptera
Family Heptageniidae Heptageniidae
Size 10-14 mm 10-14 mm
Habitat Rivers & Streams Rivers & Streams
Diet Omnivores Herbivores
Regions North America Europe
Conservation Least Concern Least Concern

Western Iron Dun

An iconic eastern mayfly that signals the start of spring fly-fishing season. Nymphs have only two tails and cling to rocks in fast current.

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Did You Know?

It was named after Theodore Gordon, considered the father of American dry-fly fishing.

Flat-headed Mayfly

A stream-dwelling mayfly nymph with a flattened body for clinging to rocks in rapids.

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Did You Know?

Its flattened nymph shape allows it to live in the boundary layer of fast currents.