Body Sparse dubbing or quill (slim, starts mid-shank)
Wing Wood duck flank (upright, divided)
Hackle Stiff cock (2-3 turns only)
How to tie it
Mount a standard dry-fly hook and start thread one third of the way back from the eye. That forward start is the defining feature of the style: the wings go well back from the eye, leaving room for a clean head.
Select a wood duck flank feather, strip the fluff, and tie the fibres in as a single upright bunch with the tips forward, one shank length tall.
Post the bunch upright with thread turns in front, then split it into two equal wings and figure-8 between them until they stand divided and slightly canted forward.
Wrap back to the bend and tie in a sparse bunch of stiff cock hackle fibres as a tail, one shank length long. Sparse is correct — a Catskill tail is a handful of fibres, not a brush.
Dub a very slim body forward, or wrap a stripped quill, starting at the bend and stopping at the wing.
Tie in two stiff cock hackles behind the wing and take two or three turns behind and two in front, no more. The style is defined by what is left off.
Leave the front third of the shank bare, build a small neat head, whip finish and cement. That open space at the eye is deliberate and is what makes the fly look Catskill.