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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

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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Dark Olive Brown Spinners

Like most common names,"Dark Olive Brown Spinner" can refer to more than one taxon. They're previewed below, along with 1 specimen. For more detail click through to the scientific names.

Mayfly Species Baetis flavistriga

These are very rarely called Dark Olive Brown Spinners.
This is one of the most widespread and abundant Baetis species, and it may produce fishable hatches under a variety of conditions.

This species is known in angling books by several old synonyms, including Baetis quebecensus, Baetis levitans, Baetis cingulatus, and Baetis phoebus, in addition to the correct name.
Dorsal view of a Male Baetis flavistriga (Baetidae) (BWO) Mayfly Nymph from the Dosewallips River in Washington
This nymph keys to Baetis assuming the villipore is present (hard to see in my photos or scope), and within that genus it tentatively keys to the flavistriga species complex, of which Baetis flavistriga itself is by far the most common in Washington state, so that's the most likely ID.

Mayfly Species Dannella simplex

These are very rarely called Dark Olive Brown Spinners.
Although by no means a superhatch, this species can be important. Authors who discuss it lament the general lack of credit it receives for the fine hatches it produces on some streams.

Dark Olive Brown Spinners

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