When Rod Haig-Brown was writing The Western Angler, he visited Paul Lake and met the then already famous William Nation, anglers guide, and through
1938 and in '39 they corresponded, mostly on fly tying and pattern development. In an April 1938 letter to Haig-Brown, Nation, mentions a plain black fly.
I enclose a very simple fly that I have worked out in imitation of the chironomids, slim black silk body, six strand of brown coast bucktail over and four under.
Sorry for the crappy picture.