Callibaetis mayflies live in lakes or very slow moving sections of rivers. They are an important hatch in the spring/summer on many bodies of water and trout can take them as nymphs, emergers, duns and spinners with reckless abandon when they are available in good numbers. The Film Critic sits low in the surface film, imitating a nymph hatching into the dun, which is a vulnerable moment for the mayfly. Flies that imitate this moment in the hatching process are often the most effective. Fish the Film Critic just like a dry fly and look for a big trout head to come up and slurp it in.