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Mayfly Species Siphlonurus occidentalis (Gray Drake)

Taxonomic Navigation -?-
Common Names
MatchCommon Name
****Gray Drake
*Black Drake
Pictures Below
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.

Pictures of 8 Mayfly Specimens in the Species Siphlonurus occidentalis:

Specimen Page:12
Siphlonurus occidentalis (Gray Drake) Mayfly NymphSiphlonurus occidentalis (Gray Drake) Mayfly Nymph View 2 PicturesThis species emerges very late in the fall often along with Siphlonurus autumnalis just before ice forms on edges of streams.
Collected November 30, 2006 from Crazy Beaver Spring in Montana
Added to by Bnewell on June 28, 2011
Specimen Page:12

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