Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
This specimen was the only one of its kind in my kick net sample from this small creek. At first I thought it was Nemouridae, but it's not. Unfortunately, there is no species key available for Taenionema nymphs. Potential species found in Washington include nigripenne, oregonense, pacificum, and pallidum.