. . . Let’s call it natural if the fly is doing something the trout are used to seeing. If the fly looks like what a trout watches day after day and hour after hour — if the fly is doing something expected — that’s a natural presentation.
By contrast, let’s call it attractive if the fly deviates from the expected norm. Like any other animal in the wild, trout know their environment. They understand what the aquatic insects and the baitfish around them are capable of. They know the habits of mayflies and midges, of caddis, stones, black nosed dace and sculpins. And just as an eagle realizes that a woodland rabbit will never fly, a trout knows that a sculpin cannot hover near the top of the water column with its nose into heavy current . . .