We got out on the Yellowstone yesterday - just after it cleared and right before it got dirty again. Cold nights of last week brought the river around to fishable shape for just a couple of days. The Caddis hatch has been intense over there and the increased visibilty brought a lot of fish up yesterday during the between 1:00-4:00. Hope for some cold nights again, but my guess is that the whole thing is over for awhile.
We saw mats of bugs for about 2 hours yesterday. I mean so thick you could skip a rock on bugs all the way across the river. We really didn't have much action until the bugs started coming off. Caddis hatches can be like that becuase the adults don't stay on the water long after hatching and the pupa's swim very quickly through the water column. So, ideally you wait until the bugs start laying eggs on the water and then the fish tend to really get on them. In the meantime, fishing a dripper off a caddis dry can find some fish pretty reliably until they get on the water. If nothing else, the presenc of that many bugs is mind boggling and a spectacular sight.