Wildlife Survey & Photo Service

Epeorus  Nymph

Epeorus  Dun

Epeorus  Spinner


Epeorus nymph clings to a rock in fast water.

Pale Evening Dun - Epeorus sp.

The Epeorus species are an interesting group of aquatic insects. They prefer fast cool water as their gills are sensitive to various types of pollution. Note the nymph on the left that is designed to withstand fast water. They use their claws and those gorgeous gills on its abdomen to hang on.


Putah Creek: No Epeorus in regular collections until 2008 when we started getting significant numbers at Fishing Access # 5 and at a restoration site near Winters.

Epeorus dun (Pale Evening Dun or Pink Lady)

Epeorus sp. (Dun or Sub-Imago Stage)

The dun stage shown on the left is the first of two adult stages that occur only in mayflies.  The duns can fly but are sexually immature and literally covered with a "shuck" that would prevent any sexual activity.

Male Epeorus Imago

Epeorus sp. (Spinner or Imago)

The spinner stage (known as Imago in scientific lingo) is one of my favorite aquatic invertebrates. They have managed to get out of the Sub-Imago shuck and are now sexually mature. I have encountered massive hatches of these beautiful mayflies while fly fishing on the West Coast. In June 2012, we witnessed a significant Epeorus hatch on the Truckee River.


To see the amazing transformation from dun to spinner, download an article I wrote for the FlyFisher on mayflies. MAYFLY PDF

Epeorus sp. Fly Fishing Pattern


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