Emergers and generally all types of flies which are fished under the surface are a significant category of artificial flies, because in cases where fish rise different insect pupae that change under the water surface in an adult, you will usually fail with a different type of flies!
The magic of these flies is that they are hung in a water blanket, and part of the fly overlooks the surface, while the other part of the fly - often even differently colored - is sunk under the water and attracts the fish at a given moment much more efficiently than classic dry fly.
Excellent patterns - especially for slow rivers and still water - are the Shutlecocks that imitate the hatching adult midgets. Once the fish collect these insect stages, Shutlecocks are a very effective weapon with great efficiency!
