Pure silk has been used as a fly tying thread for hundreds of years.  Semperfli Pure Silk has been designed to match the Edmonds and Lee silk in their book Brook & River Trouting.
 
This is a twisted  silk and can be untwisted to lay perfectly flat. Ideal for salmon patterns, North Country and Clyde style fishing flies.
 
In1854 Greenwell used pure silk as the basis of the Greenwell's Glory came to be tied, but there is no doubt silks have been used in Salmon Flies and Trout Flies for hundreds of years.
 
If we look at the Greenwells Glory which was the invention of Canon William Greenwell of Durham "I caught some of them, and came to the conclusion that the best imitation would be the inside of a blackbird's wing, with a body of red and black hackle, tied with yellow silk."