Blue-Winged Olive vs Yellow May Dun

Side-by-side species comparison

Attribute Blue-Winged Olive Yellow May Dun
Scientific Name Baetis tricaudatus Heptagenia sulphurea
Order Ephemeroptera Ephemeroptera
Family Baetidae Heptageniidae
Size 5-9 mm 10-15 mm
Habitat Rivers & Streams Rivers & Streams
Diet Omnivores Omnivores
Regions North America Europe
Conservation Least Concern Least Concern

Blue-Winged Olive

A small olive-colored mayfly with distinctive bluish-gray wings, abundant in clean streams across North America. It produces multiple generations per year.

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Did You Know?

Blue-winged olives are among the few mayflies that hatch in winter, providing vital food for trout during cold months.

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.