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Mayfly Species Attenella margarita (Little Western Blue-Winged Olive)

Pictures Below
Though having a national distribution, this species is considered by angling authorities to be important only in the West. In localized waters where it is abundant, it can be a significant hatch.  

Where & When

Region: West

Time Of Year (?): August

Hatching Behavior

Time Of Day (?): Mid-morning

Fred Arbona in Mayflies, the Angler, and the Trout says that trout prefer nymphs on the surface when the margaritas are hatching, so a floating nymph is the ideal tactic. He also says this hatch is unusually prone to producing stillborn (
This stillborn Ephemerella subvaria dun is trapped in its shuck.
This stillborn Ephemerella subvaria dun is trapped in its shuck.
Stillborn: In fly fishing, a stillborn insect is one which got stuck in its nymphal or pupal shuck during emergence and floats helplessly on the surface instead of flying away. It is a specific class of cripple, although it is sometimes used interchangeably with that term.
and crippled duns.

However, Knopp and Cormier say that this species, like Attenella attenuata, emerges on the bottom of the stream and rises to the surface as a dun. This conflicts with Arbona's observation.

It may be that the nymphs of this species make several failed trips to the surface, like most in the family Ephemerellidae do, before deciding to emerge, and that Arbona observed feeding during this behavior. Or there may be a wider range of emergence behavior during this hatch than either author realized.

Spinner Behavior

Time Of Day: Late dusk

Nymph Biology

Current Speed: Slow

Environmental Tolerance: Best in consistently cold water

Pictures of 1 Mayfly Specimen in the Species Attenella margarita:

Female Attenella margarita (Little Western Blue-Winged Olive) Mayfly DunFemale Attenella margarita (Little Western Blue-Winged Olive) Mayfly Dun View 6 PicturesI found this dun unusually late in the year for anything in the Ephemerellidae family in the East. It's also small for that family.
Collected September 4, 2006 from Willowemoc Creek in New York
Added to by Troutnut on October 3, 2006

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