A study of what rainbow trout eat shows that their diet from fingerling to about 16 inches consist mainly of insects. Which include mayfly, caddis, and terrestrial insects. I am going to tell you about the different stages in a mayflies life and how to imitate it with a fly and fly rod.
Mayflies life cycle starts as an egg deposited by an adult spinner. The eggs sink to the bottom of the stream or body of water, and hatch into a nymph. The nymph stage last a year as it grows larger and as it approaches its adult stage. Nymphs burrow in the stream bed or hide under rocks as it waits it time to become an adult. This is the phase of life that normal nymph fishing tries to replicate. As nymph prepare for adulthood they raise in mass to the waters surface where they use the surface tension of the water to shed their skin and became an adult. While they are trapped in the surface tension is the next opportunity to catch fish using emerger patterns. Once they shed their skin their newly formed wings are exposed and need to dry before they can fly off the surface of the water. This is when a dry fly is effective. They are vulnerable as they ride on the surface and dry fly fishing takes advantage of that vulnerability. When the adult flies off the water they will hang out on bushes and trees to do the final molt. This stage they are called spinners and after they become spinners they mate in the air and the females fly back to the water to deposit their eggs to start the cycle all over again, but the spinners which usually fall about dusk or later evening bring out some of the best fishing of the year as trout line up in feeding lanes sucking down spinner after spinner. When you hear of fly fisherman fishing late into the evening this is what they are trying to do, catch a spinner fall where large light sensitive trout are gorging themselves on spinners. Best Fishing gear reviews
All of the mayflies life cycles are imitated with flies fished with no action or dead drift. When you are nymph fishing you are running a nymph along the bottom imitating a dislodged nymph as it struggles to get back under cover and safety. Emergers are fished in or just under the surface film on a greased or dressed leader and just like a dry fly you cast up and across with a dead drift and watch the leader for any indication of a strike. Many people will mistake trout taking emergers as trout feeding on dry flies. If a trout actually is taking a dry from the surface the take will leave an air bubble as they suck in the fly. Use this clue to help you decide how and what you want to present to the trout, be it an emerger or a dry. Dry flies are fished upstream and you have the excitement of watching your fly as it rides the surface of the water while you wait for a strike, and spinners are fished dry the only thing new added is casting and setting the hook in the dark. Spinner fishing requires scouting the stream in the daytime so you know where every tree and bush is so you don’t find them with your fly when you are false casting at night