About Pale Evening Duns
Pale evening duns are clinger-type mayflies, so the nymphs inhabit moderate to fast flows with rocky bottoms. They are seldom available to trout until the hatch season, which ranges from June through September, depending on the locale.
When nearing maturity the nymphs migrate towards quiet water near shore, and you can drift a nymph near the bottom in these areas. Fishing the dun during a hatch is usually more productive, however. Since trout in slow water near the bank are particularly wary, your casts need to be precise and targeted to individual fish.
Spinners are important. Mating swarms gather over riffles and fast runs, and females dip their abdomens in the water to release their eggs. Spent spinners are usually swept into backeddies and other places where the current gathers drifting debris, and these are often the best places to cast a spinner imitation.