Small Square-Gilled Mayfly vs Flat-headed Mayfly

Side-by-side species comparison

Attribute Small Square-Gilled Mayfly Flat-headed Mayfly
Scientific Name Caenis luctuosa Epeorus assimilis
Order Ephemeroptera Ephemeroptera
Family Caenidae Heptageniidae
Size 3-6 mm 10-14 mm
Habitat Ponds & Lakes Rivers & Streams
Diet Omnivores Herbivores
Regions Europe Europe
Conservation Least Concern Least Concern

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.

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.