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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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Female Ephemerella (Hendricksons, Sulphurs, PMDs) Mayfly Spinner Pictures

I've seen Ephemerella invaria with green egg sacs and Ephemerella subvaria with yellow one. This one seems too large for dorothea. So what is it? I'm not sure.

Many females of this species were gathered in tight clouds to lay their eggs over the riffles in a mid-sized Pocono stream right at dusk. It would have been a fishable spinner fall if I'd stuck around to wait for them.

Female Ephemerella (Ephemerellidae) (Hendricksons, Sulphurs, PMDs) Mayfly Spinner from Mystery Creek #42 in Pennsylvania
Lateral view of a Female Ephemerella (Ephemerellidae) (Hendricksons, Sulphurs, PMDs) Mayfly Spinner from Mystery Creek #42 in Pennsylvania
Female Ephemerella (Ephemerellidae) (Hendricksons, Sulphurs, PMDs) Mayfly Spinner from Mystery Creek #42 in Pennsylvania
Female Ephemerella (Ephemerellidae) (Hendricksons, Sulphurs, PMDs) Mayfly Spinner from Mystery Creek #42 in Pennsylvania
Ventral view of a Female Ephemerella (Ephemerellidae) (Hendricksons, Sulphurs, PMDs) Mayfly Spinner from Mystery Creek #42 in Pennsylvania
Dorsal view of a Female Ephemerella (Ephemerellidae) (Hendricksons, Sulphurs, PMDs) Mayfly Spinner from Mystery Creek #42 in Pennsylvania
Ruler view of a Female Ephemerella (Ephemerellidae) (Hendricksons, Sulphurs, PMDs) Mayfly Spinner from Mystery Creek #42 in Pennsylvania The smallest ruler marks are 1 mm.
"Hunter orange" ball of eggs.  The debris sticking to it comes from my container and handling; it's not part of the structure.

Female Ephemerella (Ephemerellidae) (Hendricksons, Sulphurs, PMDs) Mayfly Spinner from Mystery Creek #42 in Pennsylvania

This mayfly was collected from Mystery Creek #42 in Pennsylvania on May 28th, 2007 and added to Troutnut.com by Troutnut on June 4th, 2007.


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Female Ephemerella (Hendricksons, Sulphurs, PMDs) Mayfly Spinner Pictures

Collection details
Location: Mystery Creek #42, Pennsylvania
Date: May 28th, 2007
Added to site: June 4th, 2007
Author: Troutnut
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