I was turning over rocks in a small mountain freestone stream yesterday and found a white, bloated looking stone fly nymph. These are small, not big Salmonfly-esque critters, think more like the early black stones, 14-16.

I have heard or seen mention of a white stonefly nymph before, but don't recall the where/when/why of this critter.

Any thoughts on this? I'm very puzzled by this little unique thing, but then again, perhaps it is I who has just opened my eyes to them....