Getting to Know The Skwala Stonefly – Fins and Feathers Bozeman
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Getting to Know The Skwala Stonefly

The Skwala Stonefly should be included in any comprehensive list of important stoneflies for the western flyfisher. Though often mistakenly thought of as members of the Perlidae (Golden Stones) that happen to hatch early, they are actually quite different and often far more important on many western rivers than their more publicized cousins. The river dwelling adults have smoky brown to brown wings, brown legs, and either primrose (often tinged w/ olive) abdomens ribbed with brown or the reverse in darker strains.

In Montana, their emergence runs for a few weeks to a month or more and can start as early as mid Febuary, depending on the year. Years with cold Januarys and/or lacking an early February “false spring” can delay them until the end March or even into mid April. Skwala are terrestrial emergers like all the larger stoneflies. What is different about them is their preference for privacy even after emergence. They are hidden in the crevices of cobble instead of clinging to open exposures of large rock or plant life. This can perhaps be explained by their emergence so early in the year before the shore cobble builds up too much daytime heat. They will go completely unnoticed by all but the most astute anglers and observers until their mating flights begin, seemingly to materialize out of thin air. In years of abundance, they can come in clouds of insects within minutes.

Their dark bodies coupled with their flush floating posture make them very difficult to make out on the water, in spite of their size. Adding to this difficulty is their placid behavior. They never seem to flex and flap wings as their larger relatives do. Their presence on shore side rocks is the first alert, followed by seeing them in the air and even crawling on you. You won’t usually see them on the water, but when you see them everywhere else and fish working, it’s time to fish the dry fly. Ovipositing flights seem to be dependent on sunshine and calm conditions which are usually not the most prevalent late Winter and early Spring here in MT. This may explain their smaller numbers after previous wet blustery seasons and the astounding populations that build up when warm drought years string together.

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