Hmmm,
Not sure of the size of it, but if a size 12 or 14 would make for "the right size" then I would use grey tying thread, dub the abdomen with a mix of black and yellow wool, the legs would be woodcock soft hackle to get the red/black barring, and a shell back over the top of the legs would be a slip from a grey mallard quill (whole thing tied as in John's spider spider in the FOTW archives).
I would not photograph it anywhere near as well as this one though!
- Jeff