Dark Hendrickson Mayfly vs Flat-headed Mayfly

Side-by-side species comparison

Attribute Dark Hendrickson Mayfly Flat-headed Mayfly
Scientific Name Leptophlebia cupida Epeorus assimilis
Order Ephemeroptera Ephemeroptera
Family Leptophlebiidae Heptageniidae
Size 8-12 mm 10-14 mm
Habitat Rivers & Streams Rivers & Streams
Diet Detritivores Herbivores
Regions North America Europe
Conservation Least Concern Least Concern

Dark Hendrickson Mayfly

A dark-bodied spring mayfly important to trout anglers in the Northeast. Nymphs inhabit leaf packs and debris in slow to moderate stream sections.

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Did You Know?

It often emerges alongside Ephemerella subvaria, and the two species together form the famed Hendrickson hatch.

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.