Mountain Flathead Mayfly vs Western Iron Dun

Side-by-side species comparison

Attribute Mountain Flathead Mayfly Western Iron Dun
Scientific Name Cinygmula ramaleyi Epeorus longimanus
Order Ephemeroptera Ephemeroptera
Family Heptageniidae Heptageniidae
Size 7-10 mm 10-14 mm
Habitat Mountains Rivers & Streams
Diet Omnivores Omnivores
Regions North America North America
Conservation Least Concern Least Concern

Mountain Flathead Mayfly

An alpine mayfly restricted to high-elevation cold streams in the Rocky Mountains. Nymphs feed on diatom films on boulder surfaces.

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Did You Know?

This species cannot survive in water temperatures above 15 degrees Celsius.

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.