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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.

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington
This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.
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 Caudatella heterocaudata Mayfly Dun Pictures

These duns were emerging sporadically throughout a cloudy evening at the end of June. Had I looked more closely when I caught this one and realized it represented my first collection of this genus, or just noticed the really striking coloration, I would have set my fly rod on shore and spent more time lurking mid-river with my net trying to catch more of them emerging (and at least one in better shape).

It's always a bit difficult to identify a female dun, but in this case the three longitudinal stripes on the sternites are very distinctive and narrow the choices to Caudatella heterocaudata and Caudatella columbiella. However, the length of the fore wing measured with a caliper is 7.25 mm, whereas columbiella should be no more than 6 mm, so heterocaudata appears to be the correct ID.

Lateral view of a Female Caudatella heterocaudata (Ephemerellidae) Mayfly Dun from the Cedar River in Washington
Dorsal view of a Female Caudatella heterocaudata (Ephemerellidae) Mayfly Dun from the Cedar River in Washington
Ventral view of a Female Caudatella heterocaudata (Ephemerellidae) Mayfly Dun from the Cedar River in Washington
Ruler view of a Female Caudatella heterocaudata (Ephemerellidae) Mayfly Dun from the Cedar River in Washington The smallest ruler marks are 1 mm.

This mayfly was collected from the Cedar River in Washington on June 30th, 2021 and added to Troutnut.com by Troutnut on July 2nd, 2021.


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Female Caudatella heterocaudata Mayfly Dun Pictures

Collection details
Location: Cedar River, Washington
Date: June 30th, 2021
Added to site: July 2nd, 2021
Author: Troutnut
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