For such a tiny insect, as the name suggests, midges are an important food source. They hatch throughout the year and become a primary source during the winter season. Commonly mistaken for a mosquito the adult midge is the stage most anglers identify. Adults have a mosquito-like appearance but differentiate by smooth glassy wings and furry antenna. Though more often, it is the pupae stage that fish key in on. Trout will sip mouthfuls at a time, sometimes appearing to take the winged adult but closer observation shows them feeding on the worm-like pupae just below the surface.
Midges transform through a complete metamorphosis. There are over a thousand various species. Larvae, typically smaller than one-quarter inch, live on the bottom of the stream or lake. Beginning pupation, pupae dislodge from the bottom and wiggle to the surface. Pupae then hang on the underside of the surface film and transform into adults. They usually hang there for long periods of time making them easy prey for trout.
Fishing the pupae effectively requires suspending either the imitation or the leader. A common approach is to apply floatant to the leader leaving the final six inches near the fly unaffected. Some pupae patterns incorporate floating materials at the head to mimic the vertical hanging angle. When applicable, it is wise to use some type of visual indicator. Popular indicator choices include a dry fly, monofilament curly cue, or foam pinch-on. Keep in mind that midge fishing is often done in the slower sections such as the rear of a pool. Because of this you may find using an indicator creates too much disturbance and is a show-stopper. Try the curly-cue or train yourself to key on the greased leader for takes. Other times trout will make it easy by creating surface disturbance of course when this happens you can forgo the indicator and set the hook. Fishing pupae and larvae in deeper water is also effective. Use nymphing tactics for these situations.
Especially during the slow season it is the mighty midge that comes to the rescue. Learn your bugs.