Scattered in among the mayfly emergences are a variety of caddis fly and stonefly hatches. On most Mountain State waters, heavy caddis and stonefly hatches are relatively infrequent, although the little Yellow Sally stonefly sometimes is the exception that proves the rule.
I've been a fly fisherman for 35 years, and I can count on the fingers of one hand the times I've exploited a heavy caddis fly or stonefly hatch. I'll say this, though - they certainly were memorable.
The best big-fish day I ever had came during a hatch of large green-bodied caddis flies on a boulder-strewn central West Virginia stream. I frankly didn't know a hatch was on, but had on the end of my line a fly that matched the hatching pupae perfectly.
In about half an hour's time over roughly 100 yards of water, I caught a 19-inch brown trout, a 13-incher, another 19-incher, and hooked and lost a mammoth brown my fishing partner estimated at 24 inches.
The most memorable hatch I ever encountered was one I couldn't fish. I was vacationing in Yellowstone National Park with my wife, and I had taken her to look at the Yellowstone River's famed LeHardy Rapids.
The National Park Service has declared the rapids a "study area" and doesn't allow fishing. Cutthroat trout there are both abundant and large.
When my wife and I were there, a flush hatch of 2-inch long stoneflies known as "salmonflies" happened to be underway. Huge trout were rising everywhere, gobbling the flies as they struggled on the churning surface.
I had a blast catching the big insects, crushing their heads, tossing them into the river and watching 20- to 25-inch cutts rocket to the surface to scarf them up.
I was watching fish and not catching them, but seldom before or since has "bug season" been quite that much fun.