Stoneflys can provide a good days fishing if you get it right. Similar to fishing a local caddis hatch, matching both size and color of the local stonefly population can make a difference  Because stoneflies spend the proportionally greatest time in the nymph stage and are most vulnerable to trout during their trip from water to land, never leave for a fly fishing destination without a solid selection of stonefly nymphs on hand These poor fliers are often blown from their landward perches into the drift, where they are helpless in the face of a waiting trout.