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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 Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington
Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
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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Skwala (Large Springfly) Stonefly Nymph Pictures

This one took an embarrassingly long time to identify, because the key I was following sent me on a wild goose chase when I interpreted the longitudinal dorsal stripe on the abdomen of this specimen as a "longitudinal pigment band." I've updated the key text on this site so that mistake isn't so easy for others to make.

Ruler view of a Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington The smallest ruler marks are 1 mm.
Dorsal view of a Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Ventral view of a Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
One of the lacinia separated from the head

Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Other side of the same lacinia separated from the head

Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington

This stonefly was collected from the Yakima River in Washington on April 24th, 2022 and added to Troutnut.com by Troutnut on April 27th, 2022.


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Skwala (Large Springfly) Stonefly Nymph Pictures

Collection details
Location: Yakima River, Washington
Date: April 24th, 2022
Added to site: April 27th, 2022
Author: Troutnut
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