(Siphlonurus occidentalis)
Characteristics
Two tails. Dark gray wings with heavy veination. The body is olive gray with dark brown markings. Spinners are more purplish with clear wings.
Timing of Hatches
June into early July. Duns emerge sporadically during mid-morning hours. Spinners fall in the late afternoon and evenings and sometimes mid-morning.
Habitat
Slow to medium fast water. The Gray Drake is an important hatch on the lower Henry’s Fork below Ashton, lower Fall River, the estuaries of the Madison and South Fork of the Madison entering Hebgen Lake, and the Upper Yellowstone River below Yellowstone Lake.
Comments
The nymphs concentrate in the margins of the stream where they crawl out to emerge. They are classified as swimmer nymphs. Consequently, the duns are not nearly as significant as the spinners. The mating flights of the spinners creates superb dry fly fishing on the lower Henry’s Fork. High water years provide the best Gray Drake activity.
Patterns
Feather Duster Nymph, Gray Drake Nymph, Gray Drake Spinner, Parachute Adams, Gray Wulff, Adams Parawulff
Hook Sizes
10 & 12