AB Fish Report
Insect Encyclopedia

Pale Morning Dun

Ephemerella inermis

Ephemerellidae

MayflyHook #16-188-12 mm body

Peak activity

JanFebMarAprMayJunJulAugSepOctNovDec

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Nymph

Robust yellow-olive nymph; interlocking gills on the abdomen.

Pale Morning Dun — Adult

Adult

Pale yellow body, light dun wings; classic PMD profile.

Habitat & hatch

Found in rivers, tailwaters, and spring creeks, most commonly in riffles and runs. Bottom-dwelling nymph; emerger mid-column; adult on surface film. Often associated with gravel and cobble. Mid-morning to early afternoon emergence; spinner falls in evening.

Timing

Individual emergence windows typically last 3 to 14 days. Strongest surface activity occurs around midday, and the afternoon.

Sources

  • AB Fish Report synthesis from peer-reviewed Alberta and western North America literature.