The Hooker and Royal Hooker Flies
The Hooker is a pheasant tail based nymph pattern devised by Rim Chung about 20 years ago. He ties it in brown with copper wire and black with silver wire, and used it extensively for many years, coupled in a two fly rig, with the RS2 as the point fly. While it was one of his most effective flies and even though he still uses it occasionally, he currently has mostly gone to his Avatar and Plebby as his more common upper fly. I created a similar fly made from DMC metallic embroidery thread 272 Blanc (which has been discontinued), that Rim dubbed the Royal Hooker. It works very well on the South Platte River, the Arkansas, and many other Colorado rivers, especially where cased caddis are present. Rim's brown and black ones work everywhere that there are mayfly nymphs, for as Frank Sawyer note, the nymphs tuck in their legs when swimming through the water and the midge nymphs do not have tails, so they may be taken for those as well as the mayfly nymphs.