The Bristle Back is a midge imitation, think of it as a midge emerger or a tiny Sulphur or BWO emerger. Fish just look at it as food. If fish are gently sipping something seemingly invisible off the surface or just breaking the surface with their dorsal they are often eating midges. Sometimes, in slack water the biggest fish will be milling about and sipping, they seem like small fish, don’t get fooled. Even in the middle of a mayfly hatch fish can be midging. Sometimes when nothing seems to be happening fish will be midging subsurface or eating midge pupae on the bottom. In all these cases, the Bristle Back works.
Generally this fly is fished in the surface film, be sure to present it without any drag. As with many “dry’ flies the Bristle Back can also be effective behind a weighted nymph near the bottom.
The Bristle Back comes in sizes 16 to 20 and three generic colors, olive, purple and tan.