The Yellow Sally

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Date: 01/01/2025

The Yellow Sally is one of the most common stoneflies that we see here in SW Montana during the summer months. They have been hatching on our local rivers for a couple weeks now and the numbers should start getting more impressive as the water temps rise. We have a great selection of Sallies in the nymph and adult dry fly here in the shop. Here is a little bit of information about the insect.

Yellow sally stoneflies, which are members of the genus Isoperla, inhabit most clean rivers, especially oxygen rich streams containing stony bottoms. Trout eagerly feed on yellow sallies when the spent insects fall to the river’s surface. As with other members of the order Plechoptera (stoneflies), the yellow sally has an incomplete life cycle, which is called hemimetabolism. The hemimetabolism life cycle includes three stages: the egg, nymph, and adult. There is no pupal stage of development in the hemimetabolism life cycle. The nymphs of aquatic insects that have incomplete metamorphosis live in the water; the adults live on the stream bank.

The body of the female measures up to about half an inch and the male is a little shorter. A female is longer because it needs room to carry her eggs. The adults has two tails, two long antennae, and two sets of wings that fold along the top of the body when the insect is at rest. The females lay their eggs by flying over the surface, dipping the tips of their abdomens into the water and releasing their eggs. The eggs fall to the bottom of the stream and begin a new life cycle. The entire life cycle, from egg to adult, takes approximately one year. The females end their lives on the surface “spent” with spread wings, helplessly floating on the water and becoming easy prey for the fish.