Bloodworm

The bloodworm is the larval stage of the Chironomid midge which is a favoured food item for brown and rainbow trout.
These flies imitate the motion of the larvae.
They can be fished on a floating line with a long leader using a dead drift and allowing the wind to take the fly through the water or on an intermediate line with a slow figure of eight retrieve.

The trout love them and so do I.