The conflicted emerger theory

as the mayfly emerges, its head wants to stay at the bottom because its safe and usual down there. But its biology is forcing it to the surface, with wings expanding out its back. To simulate this, tie with a tungsten beadhead and a foam wingcase. Split the case before tying it forward and let some cdc come out the case. This gives the fly an interesting bouyancy as it moves through the water.