How to tie the yarn-wind spinner when fly fishing

This is a mayfly imitation. When a mayfly nymph rises to the surface, splits open, and the adult mayfly emerges with upright opaque wings, fly fishers call the insect a mayfly dun and imitate it with fly patterns with upright wings, like the natural. Mayfly duns are available to trout immediately after they emerge from their nymphal shuck, but they soon fly to streamside vegetation where they once again shed their skins and emerge anew as mayfly spinners. Compared to duns, spinners have long tails, slim bodies, and clear wings.