Why does this rig work? First, high water flushes quantities of worms out of the banks and into the river, and the fish delight on these globs of protein washing downstream. Egg flies can produce strikes almost all year, even in months far removed from the spawn. With the scuba gear on, I watched trout gobble egg flies (often passing up other nymph patterns), in gin-clear, low water in the dog days of early August. The second part of the equation is that these patterns are highly visible... and unless you are a total cheater who scents your bugs (even I won't go there, and I'm pretty shameless), a subtle flash of added visibility can spell the difference between success and failure.