This fly is an emerger pattern and works best, of course, when fished during a caddis emergence which is generally most every summer evening from mid-June through August down on the Madison, assuming the weather is not too inclement. Trout will feed on these Caddis in all speeds of water, from the fastest to the slowest, but will exhibit different rise forms depending on the speed of the water they are feeding in. The slower the water the more subtle and quiet the rise form and vice versa. This throws a lot of fisherman for a loop, as they think different rise forms are produced by trout feeding on different insects. This is possible to be sure, but because of the overwhelming importance of caddis a fly like the Iris caddis should always be your first choice for evening fishing. Stick with it until you are positive the fish are feeding on another insect. This fly is dressed with floatant and fished dry, we usually fishupstream to rising fish, praying very close attention to getting a drag free drift.