Bleached Stimulators - Olive, Peacock, Royal & Yellow This standard Stimulator is one of the most popular fly patterns, the Stimulator is fished around the world. Smaller sizes can mimic Caddis Flies, while the larger sizes are taken for Stone/Salmon Flies. The Elk wing and rooster hackles keep this fly high and dry with ease. Recently there has been a move to the Rubber Leg style Stimulator so these are being phased out. Sizes: # 04 - # 18