The Light Cahill is a distinctive Catskill mayfly pattern and has been tied for over a century.  It has a longer tail made of white hackle barbs and a tapered body created with white hare's ear dubbing.  A larger white hackle is used to make the fly sit at a steeper angle in the water, and mallard flank feathers are tied upright to form two wings.
 
Hook size:  Dry Fly size 14.