The ubiquitous (I love that $10. word) Blue Winged Olive. The BWO (not a trucking company or rail line) is a very common mayfly that is on the small side (size 14-20). The nymph is a swimming type (as opposed to crawler, clinger, burrower which necessitate stouter bodies compared to the more slender swimmer) and some key factors for the nymph pattern are: probably split the difference and tie 16’s with some smaller. Keep the abdomen slim and have a slightly heavier thorax (like the guy that only does benches but not squats…the con look) and have a pronounced dark wingpad (Planet Trout reminded me of this from his observations).
If you query Google Images re BWO’s you will see mostly emergers (little, sparse ties on pupa hooks) and chunky dries (trying to put all the components on a size 18 hook) and not too many nymph patterns. Nymphs are prolific in the drifts of streams and occupy varied waters of the stream from rapids to the adjacent quieter waters. Also, BWO’s hatch several times a year so they are worth consideration as a must have pattern on the mayfly side. Not as flashy as the less frequent hex or the green drakes and PMD’s but BWO’s are early Spring fish food and again in the Fall and Winter (or if you are a hearty Winter fisher, you can simply view this as your primary Winter pattern). Other than midges, you have to agree the BWO is busy enough to be frequently available to the trout. As with other mayflies, the early hatches may be larger (say 14-16) and later smaller (16-20 or smaller). If you tie, it has to be simplistic patterns.
I think simplistic Pheasant Tail Nymphs, or Krystal Flash bodies or thread bodies with wire ribbing for segmentation will keep the body (abdomen sparse) and then a thorax slightly thicker will complete a simple pattern. A nice Scott Richmond piece re BWO’s at Westfly.
BWO DRY (KISS) From GFF