The Knudsen Spider was developed in the 'thirties by Al Knudsen for steelhead. It became a favorite of sea-run cutthroat anglers and has proven to be effective for them in both fresh and salt water. A friend of mine fishes this pattern almost exclusively in salt water and catches as many cutthroat (and coho) as anyone I know.
The original version was tied with a yellow body (Knudsen's Yellow Spider) and an abundance of mallard flank hackle tied with the fibers flowing back over the body. Most modern versions are tied with much sparser hackle, rarely more than two or three turns and in a variety of body colors (usually chenille).
Many people tried to increase the action of the hackle by "propping" it up with a ball of dubbing or tying a collar of stiff, grizzly hackle behind the mallard. Mike Kinney took this the final step when he developed the Reverse (or Reversed) Spider. In the Reverse Spider, the hackle is tied in immediately behind the eye of the hook with the tip pointing aft and the quill curving forward and down over the eye. Wind the hackle, one turn behind the last, back from the eye, for no more than three turns. Stroking the hackle forward while winding it on should help to form it into a "cone" projecting forward over the hook's eye. After the hackle is tied in I usually clip away the hackle tip and tie it in at a point on the shank just in front of the hook point to form the tail.
The chenille for the body is tied in at about the center of the hook shank and wound forward to the hook eye, reinforcing the base of the hackle and forcing it into an even more conical form. Reversing the chenille and winding back to the tail provides a nice little taper and the chenille is whip-finished and secured with a drop of head cement at this point.
Any waterfowl flank feather makes a good hackle material for this fly, as does Lady Amherst or golden pheasant tippet. Black, yellow or orange chenille is most commonly used for bodies. I tried to a insert a file with step-by step tying pictures but was unable to do so. If you send me a PM I'll send you the file.
_________________________
PS