March Brown Mayfly vs Small Square-Gilled Mayfly

Side-by-side species comparison

Attribute March Brown Mayfly Small Square-Gilled Mayfly
Scientific Name Rhithrogena germanica Caenis luctuosa
Order Ephemeroptera Ephemeroptera
Family Heptageniidae Caenidae
Size 10-14 mm 3-6 mm
Habitat Rivers & Streams Ponds & Lakes
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.

Small Square-Gilled Mayfly

A minute mayfly with distinctive square-shaped gills on its nymphs. Adults swarm in enormous numbers near water at twilight.

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Did You Know?

The enlarged second gill plate acts as a protective cover over the remaining delicate gills.