March Brown Mayfly vs Yellow May Dun

Side-by-side species comparison

Attribute March Brown Mayfly Yellow May Dun
Scientific Name Rhithrogena germanica Heptagenia sulphurea
Order Ephemeroptera Ephemeroptera
Family Heptageniidae Heptageniidae
Size 10-14 mm 10-15 mm
Habitat Rivers & Streams Rivers & Streams
Diet Omnivores Omnivores
Regions Europe Europe
Conservation Near Threatened Least Concern

March Brown Mayfly

A spring-emerging mayfly with a brownish body and two tails, historically important to European fly fishing. Its flat nymphs cling to rocks in fast water.

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Did You Know?

This species has declined significantly in many European rivers due to pollution and is now considered an indicator of water quality.

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.