Light dun hen and red
Local brookies take this fly with special emphasis and even more in the summer months.
What is it that mimics? The answer is mere speculation, We know that in the case of SHF spectrum is wide but the truth is that it works very well.
Perhaps all depend on your particular idea when you present these flies. I leave you the recipe:
Hook: Mustad 3906 #14/#12/#10
Thread: UNI thread 8/0, red color
Body: Kreinik red floss
Hackle: Good quality light dun hen