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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 Grammotaulius betteni (Limnephilidae) (Northern Caddisfly) Caddisfly Larva from the Yakima River in Washington
This is a striking caddis larva with an interesting color pattern on the head. Here are some characteristics I was able to see under the microscope, but could not easily expose for a picture:
- The prosternal horn is present.
- The mandible is clearly toothed, not formed into a uniform scraper blade.
- The seems to be only 2 major setae on the ventral edge of the hind femur.
- Chloride epithelia seem to be absent from the dorsal side of any abdominal segments.
Based on these characteristics and the ones more easily visible from the pictures, this seems to be Grammotaulius. The key's description of the case is spot-on: "Case cylindrical, made of longitudinally arranged sedge or similar leaves," as is the description of the markings on the head, "Dorsum of head light brownish yellow with numerous discrete, small, dark spots." The spot pattern on the head is a very good match to figure 19.312 of Merritt R.W., Cummins, K.W., and Berg, M.B. (2019). The species ID is based on Grammotaulius betteni being the only species of this genus known in Washington state.
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 Skwala nymph still has a couple months left to go before hatching, but it's still a good representative of its species, which was extremely abundant in my sample for a stonefly of this size. It's obvious why the Yakima is known for its Skwala hatch.

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
Ruler view of a Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington The smallest ruler marks are 1 mm.
Artistic 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

This stonefly was collected from the Yakima River in Washington on February 18th, 2023 and added to Troutnut.com by Troutnut on February 21st, 2023.


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Skwala (Large Springfly) Stonefly Nymph Pictures

Collection details
Location: Yakima River, Washington
Date: February 18th, 2023
Added to site: February 21st, 2023
Author: Troutnut
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