The light cahill fly pattern is an essential for fishing in the Midwest and New England areas, but it is surely not limited to there. I use this fly regularly during a variety of hatches here in Idaho with great success. This pattern so closely resembles many insects found in rivers all over the world. Originally tied by Dan Cahill using wood duck flank feathers, we now typically tie it using mallard feathers for the wings. This is a great general fly pattern and would go well in any fly box anywhere in the world where trout reside.
Originally tied by Dan Cahill for use in the Catskill mountains of NY state, this versatile dry fly will work all around the world. It does a great job of mimicking a variety of natural mayflies on the river.