Stonefly Overview

Overview: Stoneflies are a diverse group of aquatic insects found in clean, cold, fast-moving waters worldwide. Recognized for their importance to trout diets, they are present in various sizes and colors, ranging from small winter species to large, iconic hatches like the Salmonfly. Stoneflies are known for their dual life stages—nymphs, which inhabit riverbeds, and adults, which emerge and mate near stream banks. Fly anglers value stoneflies for their role in some of the most exciting nymphing and dry-fly fishing opportunities.

Nymph Stage: Stonefly nymphs are robust and range from 1/2 inch to 2 inches in length, depending on the species. Their bodies are elongated with well-developed legs, gills, and two tail filaments. Coloration varies but often includes shades of black, brown, olive, or golden yellow. Common hook sizes for imitations range from size 4 to 16, with larger sizes for species like Salmonflies and smaller sizes for winter and early spring stoneflies. Drift nymphs close to the bottom, often with added weight, targeting riffles, runs, and edges where nymphs naturally inhabit.

Adult Stage: Adult stoneflies are medium to large insects with slender bodies, long legs, and membranous wings that fold flat over their backs. Sizes range from 1/2 inch to 3 inches, with colors varying by species, including black, brown, yellow, and orange. Dry fly imitations are tied on hook sizes 4 to 16, matched to the specific species. Fish adult patterns near shorelines, focusing on egg-laying adults skittering on the surface or those blown onto the water. Hatches often trigger aggressive trout feeding, especially during sunny afternoons or early evenings.