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Photo#1752202
Ephemeroptera - Ephemerella dorothea

Ephemeroptera - Ephemerella dorothea
Mammoth Lakes, Mono County, California, USA
August 13, 2019
Size: 9.57mm
Collected on Convict Creek. Sampling the larvae from the same creek, we have found mostly Ephemerellidae, Baetidae (Baetis and Diphetor) and Heptageniidae (Epeorus). We are now looking into the emergent adults and I would like to know the family and maybe even genus of this individual. If you could provide details for why you came to your conclusion so I can begin to learn key markers for different taxa, that would be great. Thank you!

Images of this individual: tag all
Ephemeroptera - Ephemerella dorothea Ephemeroptera - Ephemerella dorothea Ephemeroptera - Ephemerella dorothea

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Ephemerella dorothea infrequens
Hi gabbyd-

Mayflies are generally categorized (by nymphal behavior) into four separate groups: Swimmers, Crawlers, Clingers, and Burrowers.
Please see Mayfly.

Swimmer mayflies known from Convict Creek are of family Baetidae.
Crawler mayflies known from Convict Creek are of families Ephemerellidae and Leptophlebiidae.
Clinger mayflies known from Convict Creek are of family Heptageniidae.
There are no burrower mayflies known from Convict Creek.

Regarding the "key markers" of the winged lifestages of the (above) listed mayfly families, the most easily observed are number of tails, and size and shape of hind wings.

The Baetids have 2 tails, and either minute hind wings, or are absent hind wings. Ephemerellids have 3 tails, and small hind wings, perhaps 1/4 the length of their fore wings. Leptophlebids have 3 tails, and small hind wings, perhaps 1/4 the length of their fore wings with rounded costal angulation. Heptageniids have 2 tails, and medium sized hind wings, perhaps 1/3 the length of their fore wings.

So, with regard to this submission, its 3 tails rules out families Baetidae and Heptageniidae, leaving only families Ephemerellidae and Leptophlebiidae. And the shape of its hind wings, being of sharp (rather than rounded) angulation identifies it as being of family Ephemerellidae.

I believe this female (based on the small eyes and the absence of male genitalia) subimago (based on what appears to me to be non-wettable hairs on the trailing edge of the right forewing) to be Ephemerella dorothea infrequens.

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Thanks
I hate it when that happens. :)

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