mark, here’s a fly recipe from Fly Fisher’s Paradise in State College, PA for a dark sulphur nymph.
http://www.flyfishersparadise.com/articles_display.php?category=Fly_Patterns&archive=true
* Hook: TMC #5262, #12-16
* Thread: 6/0 black unweighted, 6/0 brown weighted
* Weight: Fine lead wire, if desired
* Tail: Brown partridge or brown speckled hen fibers
* Body: Blend of 50% dyed brown Australian opossum and 50% orange sparkle yarn
* Wingcase: Doubled thickness of turkey tail quil
* Legs: Brown partridge or brown speckled hen fibers, tied in front of and to either side of the thorax