A few posts ago I talked of a new to me silk thread that was available. The name of that thread is Ephemera. It's a fine thread and it's colors are deep. The thread works quite nicely and it's diameter is thin but it has strength and does not break when some muscle is applied. I have also found it to be break resistant when it accidentally hits the hook point. I have three spools of thread pictured above. The one on the right is YLI silk, the center is Ephemera silk and on the left Uni thread.
Here are some Partridge and Green soft hackle flies. These are all tied with Ephemera silk. In Sylvester Nemes book "The Soft-Hackled Fly" he lists two recipes of this fly, one with a thorax and one without. These are tied with a thorax of hares ear dubbing.