With their upright wings, mayflies are the easiest to see floating on the water. And it is possible that fly fishing itself was born when early anglers first observed trout feeding on these highly visible flies. Based on behaviour and body shape, mayfly nymphs are divided into four groups- burrowers, clingers, crawlers and swimmers. Nymphs go through 20 -30 molts as they grow, and between the last few molts the wing pads darken and the wings develop. At emergence most mayfly nymphs swim or drift to the surface and emerge as adult flies. Adults go through two phases. The first commonly called a dun and the second phase being a spinner.
