**Mayfly Species Siphlonurus occidentalis (Gray Drake)**

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Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Siphlonuridae (Gray Drakes)

» Genus Siphlonurus (Gray Drakes)

» Species occidentalis (Gray Drake)

Common Names

Match	Common Name
	Gray Drake
	Black Drake

Pictures Below ↓

This is page 2 of specimens of Siphlonurus occidentalis. Visit the main Siphlonurus occidentalis page for:

The behavior and habitat of Siphlonurus occidentalis.

Pictures of 8 Mayfly Specimens in the Species Siphlonurus occidentalis:

Specimen Page:12

Male Siphlonurus occidentalis (Gray Drake) Mayfly Spinner

View 6 Pictures

Collected July 31, 2020 from the Henry's Fork of the Snake River in Idaho
Added to Troutnut.com by Troutnut on August 17, 2020

Female Siphlonurus occidentalis (Gray Drake) Mayfly Spinner

View 9 Pictures

Collected July 31, 2020 from the Henry's Fork of the Snake River in Idaho
Added to Troutnut.com by Troutnut on August 16, 2020

Female Siphlonurus occidentalis (Gray Drake) Mayfly Spinner

View 5 PicturesThis specimen was identified by association with this male.

Collected July 31, 2020 from the Henry's Fork of the Snake River in Idaho
Added to Troutnut.com by Troutnut on August 16, 2020

Male Siphlonurus occidentalis (Gray Drake) Mayfly Spinner

View 6 PicturesThis specimen was easy to key to species using the old keys in < id="115" />, and was the basis for IDs of several other Siphlonurus specimens of the same species collected on the same day.

Collected July 31, 2020 from the Henry's Fork of the Snake River in Idaho
Added to Troutnut.com by Troutnut on August 16, 2020

Female Siphlonurus occidentalis (Gray Drake) Mayfly Dun

View 6 PicturesI caught this specimen two days' walk from my macro lenses, but I don't think I have a dun of this species yet, so I took the best photos I could with my iPhone.

Collected August 30, 2020 from Island Lake in Wyoming
Added to Troutnut.com by Troutnut on September 18, 2020

Specimen Page:12

Jargon Defined:

Dun: Mayflies have two adult stages. They first emerge from the water as duns (scientifically known as the subimago stage). They then molt into the spinner (imago) stage, in which they mate and die. Sometimes the word "dun" is confusingly used to refer to a brownish gray color in fly tying materials.

Useful References:

Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.

Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.

Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.

Schwiebert, Ernest G. 1955. Matching the Hatch. MacMillan Publishing Company.

Swisher, Doug and Carl Richards. 2000. Selective Trout. The Lyons Press.