Midges are some of the most prevalent insects in many trout streams, and it's a good idea to have a good stock of different patterns. The CDC Midge Emerger is a great pattern both fished below a dry fly or nymphed deep below an indicator. Tie this pattern in multiple colors in sizes 14-22.
Hook: Tiemco 2487 or 2457, Daiichi 1130
Bead: Midge Glass Bead or Brass Bead
Thread: 70 Denier
Body: Small D-Rib
Thorax: Superfine or Ice Dubbing