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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Dorsal view of a Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington
This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Female Baetidae (Blue-Winged Olive) Mayfly Spinner Pictures

This species is probably in Centroptilum, Cloeon, or Procloeon. I captured this spinner on the same night as a dun which is probably of the same species.

Lateral view of a Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
This picture shows the shape of the costal process on the hind wing pretty well.

Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Ruler view of a Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York The smallest ruler marks are 1 mm.
Ventral view of a Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Dorsal view of a Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
This false-color image of the clear wings shows all the veins.

Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York
Female Baetidae (Blue-Winged Olive) Mayfly Spinner from the West Branch of Owego Creek in New York

This mayfly was collected from the West Branch of Owego Creek in New York on August 9th, 2006 and added to Troutnut.com by Troutnut on August 11th, 2006.

Discussions of this Spinner

No Help
Posted by Taxon on Aug 11, 2006
Last reply on Aug 11, 2006 by Taxon
Jason-

The single detached intercalaries in the fore wing would limit the choices to the genera you suggest. The sharply pointed costal projection and single longitudinal vein in the hind wing probably narrow it to a single species. Unfortunately, none of the Baetidae hind wing illustrations to which I have access show either that sharply pointed of a projection or the single longitudinal vein, let alone in combination with one another.
Anyone want to weigh on on the ID here?
Posted by Troutnut on Aug 11, 2006
Last reply on Aug 11, 2006 by Troutnut
I can't follow the key in Merritt & Cummins very far since it's not a male spinner. The sharp costal process could be a good hint. Anybody know which genus or species this is?

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References

Female Baetidae (Blue-Winged Olive) Mayfly Spinner Pictures

Collection details
Location: West Branch of Owego Creek, New York
Date: August 9th, 2006
Added to site: August 11th, 2006
Author: Troutnut
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