I notice a great many of you are consistently researching the Siphlonurus mayfly. Take a look at the attached link re Polly Rosborough, the late and great, from South Central Oregon. HIs ‘fuzzy nymphs’ were simple, impressionistic patterns. Amongst the patterns are simple black/gray drake patterns for those slow stretches of rivers, streams and sometimes lakes. A swimmer nymph that usually emerges via swimming and then attaching to weeds and reeds much like damsels..the link is worth a look at. Many current, notable tyers in the NW have always paid homage to Rosborough, so he must have known something. My favorite of his patterns was the Casual Dress.

http://montana-riverboats.com/Pages/Fly-Tying/Polly-Rosborough/index.html