I've seen trout pass up a broad variety of natural insects drifting on the stream but I've never seen one pass up a natural Inchworm. Ed Shenk and I found a large brown trout feeding below a low-hanging willow tree on a small Pennsylvania stream but he would not take any of the flies we drifted over him. Find Ed said, "Let me try something." He put on a size 14 Inchworm and delivered it with a splat. That big brown turned and took it solidly. This "splat presentation" delivered with a roll cast is very effective as is an upstream dead drift with a gentle twitch action for brown trout, brook trout and rainbows.
I was in the Shenandoah National Park early this week and had great fishing. The water temperature was running around 60 degrees. In addition to the Murray's Inchworm size 14 listed above, the Murray's Flying Beetle size 16 and Mr. Rapidan Ant size 16 are working well. The streams that I was fishing had good water levels but still be careful on your approach so you are not spooking the fish.
If you need help on stream access, see my book Trout Fishing in the Shenandoah National Park or stop by the fly shop. We will be open normal hours July 1 (9 to 4) and July 2 (9-3). We will be closed July 3-5 for the holiday. Please be sure to pick up all trash and follow the rules of the Park--no open flame fires.