Stoneflies with Color

Guest Blogger: Clay Cunningham, Cody WY, Former National Park Superintendent

Pteronarcy californica stonefly

In the Western waters when the Pteronarcy californica stonefly hatches, the fish abandon any elusiveness they may have possessed. Known as the Salmon Fly, it is one of the largest of the stoneflies. During the hatch if you didn’t see one land on you, you might think it was a bird. In the Yellowstone drainages the hatch can begin from the end of May to early June. This varies throughout the park depending on the water temperature at different elevations of the park. At higher elevations, a close relative of the californica species, the princeps species will hatch later than the californica.

The Salmon fly Pteronarcy californica spend up to three years as a nymph before emerging. During the months prior to the hatch in any one year there are three sizes of nymphs under the water in various stages of development. The nymphs are often the most numerous species in Western rivers and streams. It is wise to have some imitation of these prolific nymphs. After the hatch, there are two sizes that remain until their complete development. Just prior to a hatch, the generation that is about to hatch migrate from their rocky hiding places to shallow water where they eventually crawl out of the water and attach to nearby rocks or vegetation. That is where their husks split open and the wings emerge. It is the clumsy flying egg laying females that fly low over the water or settle on the water and deposit their egg’s while the fish are voraciously feeding.

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