Grey Duster
Blue-grey rabbit fur dubbed rough under a badger cock hackle, with a few badger fibres for a tail or none at all — Greenhalgh gives the tails as optional, and plenty of tyers leave them off. Possibly the most useful dry fly ever tied in Britain, and certainly the one most often reached for when nobody can work out what is going on: it passes for an olive, a midge, a small sedge or a nondescript terrestrial depending on the size you tie it.
Any time you cannot identify what is hatching, and as a searching fly over water where nothing is showing. Go small before you change pattern — in an 18 it is one of the best answers there is to a caenis fall, which is the hatch that otherwise beats everybody.
The badger hackle’s dark centre and pale tips break up the outline into something that reads as legs and wings without committing to either. Deliberately imprecise, on the principle that a fly which could be several things beats one that is precisely the wrong thing.
