A Heptageniidae, or pale evening dun, male spinner from the Metilious River near Camp Sherman, Oregon.  Photo shot July 9, 2010

A swarm of millions of mayfly spinners (Trycorythodes sp. in this case) clouds the air.

A trico dun above, molts into a spinner.  Below, the empty shuck of the dun sits next to the new spinner.

The male spinner (left) shows typical differences in color and eye size from the female (right).

A mayfly spinner glides gracefully down through the air.