I recall last Summer having good success along the riffles of the McKenzie River while fishing separately a nymph (Large Hare’s Ear, size 8-10) and also a Green Rockworm Larva pattern. I am going to experiment in the months ahead with dredging a shorter line, while offering two flies at once through the riffles. I will probably stay with a larger, weighted, Gold Bead Head, Gold Ribbed, Hare’s Ear for the Yellow Sally Nymph (Family Perlodidae/Genus Isoperla) and a version of the Green Rockworm larva (Caddis, Genus Rhyacophila). The Jersey Angler provides a worthy pattern for the Green Rockworm and some good pictures of the larva and his pattern The Cooper Bug.
Employ the standard nymphing rig, cast/lob/sling with a more open loop to avoid tangles of two flies, strike indicator if you use one and split shot (that would be a mess wouldn’t it?). Certain Czech Nymphs would also provide excellent pattern options for the Green Rockworm Larva.
I suggest the two patterns in one offering because they inhabit the same waters and are equally vulnerable to drift and are active during the same span of Summer. If the two fly rig is two cumbersome then keep both insects in mind for subsurface presentations, and of course, watch for the activity on the surface as Caddis come off or the Yellow Sally comes off (if you research the literature re Yellow Sally’s ‘emerging’ it is often said then crawl toward shore or up onto rocks to hatch as most Stoneflies do…. however, there are some members of the Yellow Sally that emerge out of the water like a Mayfly on the run…I witnessed this last year on the McKenzie River and commented re that back then). Regardless, have your Elk Hair Caddis and larger, cream colored wet fly or Stimulator like patterns available for surface activity too.