Nymphs have the potential to be the most useful flies a trout fisherman has in his box, because there are nymphs available in a trout stream or pond twelve months a year. Dry flies are useless to the fisherman unless there are insects hatching to interest the trout in surface food, and even during a hatch when the fish are feeding on the surface they also take nymphs below the surface.
Caddis   Stonefly   Mayfly   Attractor   Terrestrial