I remember this hatch well from when I lived in Northeast Pennsylvania. It is common all over that part of the country. It is really what the oldtimers used to call the Grannom caddis. The fly really is a very dark brown-olive in coloration with with dark grey to brown wings. A brown-olive elk hair caddis tied with either brown or olive dyed grizzly hackle is excellent for imitating this hatch. The old Grannom and the Hennryville Special also imitate this fly well.