Mayfly Species Attenella attenuata (Blue-Winged Olive)

Where & when

This species begins to emerge in Pennsylvania in early June, and good hatches last through early July in the Catskills. In the Upper Midwest it continues into August.

Hatching behavior

These mayflies emerge on the bottom of the stream and rise to the surface as fully formed duns. Trout relish the subsurface emergers and are sometimes selective to emergers only. Often they feed on the duns, too, which ride the water for an unusually long time to dry their wings.

Just like Drunella mayflies, Attenella attenuata duns rapidly change color after emerging. They start out bright green and fade into a dull medium olive color. Anglers should imitate the initial color.

This species produces a high number of cripples.

Spinner behavior

These mayflies return as spinners within two days after emerging.

Their spinner falls can provide good action, especially since they're found at a time of year when little else is on the water. The specimens I photographed belong to a hatch whose spinners produced good dusk rises for me several times late one July.

Nymph biology

Fred Arbona writes in Mayflies, the Angler, and the Trout that the nymphs live in the "silted sections of large rivers." In Mayflies: An Angler's Study of Trout Water Ephemeroptera , they are said to inhabit "gravelly riffles adjacent to slack water on streams and riffles of all sizes." Ted Fauceglia's Mayflies lists a variety of habitats, and my own experiences seem to support this idea.