Large Dark Olive Mayfly vs Small Square-Gilled Mayfly

Side-by-side species comparison

Attribute Large Dark Olive Mayfly Small Square-Gilled Mayfly
Scientific Name Baetis rhodani Caenis luctuosa
Order Ephemeroptera Ephemeroptera
Family Baetidae Caenidae
Size 6-10 mm 3-6 mm
Habitat Rivers & Streams Ponds & Lakes
Diet Omnivores Omnivores
Regions Europe Europe
Conservation Least Concern Least Concern

Large Dark Olive Mayfly

The most common European mayfly, emerging year-round in many rivers. It is a small olive-brown species that serves as a staple food for stream fish.

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Did You Know?

This mayfly can produce up to three generations per year, making it available as fish food in every season.

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.