Yellow May Dun vs Flat-headed Mayfly

Side-by-side species comparison

Attribute Yellow May Dun Flat-headed Mayfly
Scientific Name Heptagenia sulphurea Epeorus assimilis
Order Ephemeroptera Ephemeroptera
Family Heptageniidae Heptageniidae
Size 10-15 mm 10-14 mm
Habitat Rivers & Streams Rivers & Streams
Diet Omnivores Herbivores
Regions Europe Europe
Conservation Least Concern Least Concern

Yellow May Dun

A bright sulfur-yellow mayfly common across European rivers during early summer. Its flat nymphs are adapted to fast-flowing water on stony substrates.

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Did You Know?

The striking yellow color of this mayfly makes it one of the most easily recognizable species on European rivers.

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.