How to tie a Snow Fly ~ Winter Stone. This Little Black Winter Stonefly is a perfect imitation of a juvenile stonefly hatched the Summer before. I call this pattern a Snow Fly and I use it on the river when the snow flies. This Stonefly Pattern is relatively smaller than most, but all stoneflies have to be this small at some point. I like to use a size #16 or #14 hook and sometimes I will use a little bit of flash material. The Roaring Fork River in Colorado is full of Little Black Stoneflies and the fish seek them out. If you would like to catch willing trout, consider taking a fishing vacation to Aspen or near by. You will have a great time, the fishing is as good as it gets! Go to riplips.com for information and booking.