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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.

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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Little Black Caddisfly

Like most common names,"Little Black Caddis" can refer to more than one taxon. They're previewed below, along with 2 specimens. For more detail click through to the scientific names.

Caddisfly Genus Glossosoma

These are often called Little Black Caddisfly.
The sporadic emergence of these caddisflies diminishes the importance of the freshly emerged adults and pupae, but they have unique periods of vulnerability as larvae during the day and again as diving egg layers at dusk that can make them very important. A taxon can only have one common name attached in the title but this is one of those genera whose species come in a variety of colors and descriptive common names. In the West their bodies generally come in tan to brown shades with matching wings, their wings can be speckled grayish tan or even almost black as with an eastern species. Some western rivers have astounding populations. See Glossosomatidae for more information.
Glossosoma (Glossosomatidae) (Little Brown Short-horned Sedge) Caddisfly Adult from the Big Thompson River in Montana
Dorsal view of a Glossosoma (Glossosomatidae) (Little Brown Short-horned Sedge) Caddisfly Larva from the Yakima River in Washington
I caught this tiny larva without a case, but it seems to key pretty clearly to to Glossosomatidae. From there, the lack of sclerites on the mesonotum points to either Glossosoma or Anagapetus. Although it's difficult to see in a 2D image from the microscope, it's pretty clear in the live 3D view that the pronotum is only excised about 1/3 of its length to accommodate the forecoxa, not 2/3, which points to Glossosoma at Couplet 5 of the Key to Genera of Glossosomatidae Larvae.

Caddisfly Species Brachycentrus occidentalis

These are sometimes called Little Black Caddisfly.
Gary LaFontaine tells the story in Caddisflies of how this species came to awareness through rumors of a widespread, intense hatch of an undentified brown and green caddisfly throughout the West. He traveled across the West collecting these flies and determined that they were Brachycentrus occidentalis.

Caddisfly Species Brachycentrus nigrosoma

These are very rarely called Little Black Caddisfly.
This is a smaller, darker cousin of Brachycentrus numerosus.

References

Little Black Caddisfly

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