This is a most versatile pattern as you can just change the throax color and hook size to imitate all of the different mayflies in their emergent state.
It's one of my go-to patterns all year 'round. Tie some up for the fall on a size #12 hook, with a reddish brown dubbed thorax - this imiates the Slate Drake (Isonychia) quite well.
And sharpen your hooks! You'll catch more fish.