This specimen is on the left in this picture. On the right is another one I collected but didn't otherwise photograph. It's from the same stream and time, and presumably of the same species. It shows quite a bit of natural variation.
Female Leptophlebia (Black Quills and Blue Quills) Mayfly Dun from Factory Brook in New York
Troutnut.com is a collection of pictures and information about fly fishing. Fly fishermen, fly tiers, and trout enthusiasts of all stripes can learn more about life beneath the surface of trout streams, as well as how to better imitate aquatic insects with artificial flies to catch trout. There are aquatic insect pictures, underwater pictures, landscape pictures, and a comprehensive reference to the common names of trout stream insects.