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

Mayflies

Caddisflies

Stoneflies

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

This is the main Western species of Siphlonurus, and probably the most productive species of that genus in America.

Where & When

Region: West
Time Of Year (?): April to October; peaking in August and September
Altitude: 3,000 to 5,000 feet

This species most abundant in the late summer and early fall when few other mayflies are on the water. Its activity may last few months in a single location. There's a good chart in Knopp and Cormier's Mayflies: An Angler's Study of Trout Water Ephemeroptera detailing where and when to find this species.

Hatching Behavior

Time Of Day (?): Midday

The emergence is relatively unimportant because the duns usually cawl out onto shore to hatch, but shallow nymphs may be effective when this activity is at its peak.

Spinner Behavior

Time Of Day: Mid-morning or evening

The spinners are the most important stage of this hatch.

Your Thoughts On Siphlonurus occidentalis:

You must log in at the top of the page to post. If you haven't registered yet, it's this easy:

Underwater Pictures
Landscapes & Trout
Desktop Backgrounds
Fly Tying Contests^*

Articles & Links
Common Names
Video Clips
Alaska Pictures^*

New features!

Jargon Defined:

Duns: 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.

Emergence: The transformation of a nymph or pupa into the adult winged stage of an insect. The term may refer to the emergence of an individual, or the daily or yearly event in which all individuals of a species emerge.

Nymphs: The juvenile, underwater stages of mayflies, stoneflies, dragonflies, and damselflies and other aquatic insects whose juvenile stages are covered by hard exoskeletons. The word can also refer to the fishing flies which imitate these creatures, in which case it is used as a blanket term for flies imitating any underwater stage of an invertebrate (except for crayfish and leeches).

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.

Top 10 Hatches

»

Baetidae

»

Ephemerellidae

»