I have seen that behavior on many times on catskill rivers and the streams in Western NY. It almost always is related to caddis activity. Apparently as caddis pupae hatch they make a mad dash toward the surface. This rapid ascent apparent triggers a chase condition as the fish move toward the surface often taking the fly prior to breaking through the surface. I have always had a difficult time catching fish during a caddis hatch. What works for me most often in this situation is a softhackle dead drifted and then lifted toward the surface in a leisering lift type of manuever. I have tried the bubble caddis that LaFontaine made so popular but that never worked for me. A soft hackle with a little antron or something coming from the tail end to look like bubbles as the fly swings up seems to be a pretty good response in that situation.
Now that we met and got to chat a little bit up near Elkmont you can see that I am an absolute novice - don't forget the raingear - and know very little about entomology, BUT I did stay at a Holiday Inn Express last night.
Talk to ya soon.