Those "Hackled Haystacks" in dark tan with a brown wing are my favorite Hecuba pattern on Yellowstone River floats. Eight years ago, you never saw Hecubas. Five years ago you started seeing a few in lower Paradise Valley. Three years ago were the first heavy hatches on the upper Yellowstone near Gardiner. A regular Sparkle Dun just can't float long in the rough water up there. I tie those for personal and client use with a speckled badger saddle that might as well be worth its weight in gold.
Interesting how the Henry's Fork Flavs are basically olive/yellow, just like the Green Drakes. 90% of both we see in the northern part of YNP are much more gray-olive.
Owner, Yellowstone Country Fly Fishing
Head Guide, Parks' Fly Shop
Fly Designer, Montana Fly Company
Author, Yellowstone Country Flies and River Characters