The Chironomid Pupa Red Gold Bead is used to imitate a red midge or red chironomid, which are abundant in many rivers and lakes. This bug is enthusiastically targeted by trout, and this fly will catch them!
I've had success year round using this for wild trout in mountain streams in the southern Appalachians. The bite seems best with higher and slightly turbid water. This is also, IMO the best nymph for sunfish. Use on a dropper under a fluffy/foamy dry and fish over submerged weeds, thick silt, or leaf strewn bottoms.