If the famous fly tier, Frank Sawyer, concluded that nymphs never extended their legs when moving away from the bottom why do we persist In tying legs on our flies? He concluded that free swimming nymphs simply let their legs hang against their bodies.
In the literal sense yes. While actually swimming, an exact copy would have legs kept tight. However, when tying in the impressionistic sense, legs can give the impression of a struggling nymph or even Gill movement. I’ve never found movement in a nymph pattern to be a detriment.
Mr. Sawyer was primarily speaking of blue wing olives, which are fine swimmers. Many of the nymphs that we attempt to imitate are not so good at it. They do their best to reach the surface, or bankside structure, but vary in their swimming abilities. Also, many nymphs are dislodged from the bottom, or are part of natural drift, and are not swimming to the surface. They likely have their legs akimbo, not tucked into their cute little nymphy selves.
Chuck
I go along with Ralph on the movement theory. We are trying to imitate living creatures that move in some way or another at various times in their life. I believe any materials we can incorporate into our nymph imitations that move have to look more lifelike and add to their fish attraction - be it picked out dubbing, rubber legs, CDC, marabou, whatever. That’s why, I think, realistic imitations that look exactly like the real nymph but with hard, stiff materials are many times (or most times) not as effective as nothing more than a hook covered with a little dubbing and a wrap or two of soft hackle that don’t resemble anything alive, except that they have movement.
Joe
I think CHuck is on the mark here. It really depends on the type of mayfly nymph. For Baetis, BWO, nymphs, I omit the legs (or even a picked out thorax) as the naturals are thin and good swimmers. For others that are more of the clinger variety, March Browns come to mind, the legs are pretty prominent and probably bear representation in some manner.