But.
You posted an ento pic to support your position which seems unfair as a picture is a more powerful persuader than language. 
It seems...many nymphs captured and photographed are not usually at the hatch-ready phase where their wing cases would become a prominent feature. Again, I'm simply riding on the shoulder of someone who is playing devil's advocate and put little faith in any single attribute. I'm quite happy with flies striving for some physical imitation or ignoring physical imitation in preference of vitality. However, wingless wets, unless weighted, are presented fairly high in the water column and if tied to represent an emerging or hatching nymph, would possess a dark/darkened wing case, in some cases. In terms of imitating naturals, I think you've hit on the same point as accentuating the underbody. In terms of the pics found online of nymphs...I think they make a very strong argument for the use of game birds. The legs, tails, buggy bodies. It is no wonder grouse, partridge and woodcock were so often used in tying the spiders. I don't think I even tie many flies with a discernibly darker thorax, but I usually look for contrast and vitality, and your representation here has that in spades. It's a damn nice fly. Thanks.
w
thanks, Carl, but what I said is absolutely true, you chaps are very knowledgeable and skilled.
) pushed down on with a finger or thumb. This devious accident could potentially result in a darker wingcase without tying additional bits in. The only additional problem to contemplate besides potentially not making it to flymph heaven for having the thought to begin with is how to make the wingcase pronounced/humped, I might start using uv glue as head cement. 
