Gary Lafontaine had this fly
Rollover Scud
HOOK: 14-18; TMC 9300?standard wet fly hook
WEIGHT: strip of lead wire (tied on top of the hook shank)
BACK: eight pieces of Fluorescent Blue Stren spinning line
BODY: Antron dubbing (dubbed rough and shaggy)
The fly, unbalanced by the strip of lead along the top of the hook shank, flips over when it isn't being retrieved. This is one of the few patterns that will make trout that are "grazing" on zooplankton strike an artificial?the sudden roll of the fly triggers a reaction. It is an indispensable pattern on rich lakes with populations of real scuds. It is a valuable searching fly even on infertile lakes, where trout never saw a scud but still respond to the rolling action of the fly. Olive and orange are the best colors for the Rollover Scud.
I read about this somewhere in detail , but I found the reciepe here on FAOL