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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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Male Cinygma dimicki (Western Light Cahill) Mayfly Spinner Pictures

A couple days earlier I caught a male spinner of this species with some wing damage and missing tails, so I went back to the same pool try to get one more intact. This one has some leg damage, but between the two specimens you can get an idea what the whole insect looked like. There were small clouds of Cinygma dimicki spinners again over the same two small, specific locations in the pool, which is an interesting testament to how repeatably they choose their ideal mating habitat. I was able to capture this one and a female.

Lateral view of a Male Cinygma dimicki (Heptageniidae) (Western Light Cahill) Mayfly Spinner from the Cedar River in Washington
Male Cinygma dimicki (Heptageniidae) (Western Light Cahill) Mayfly Spinner from the Cedar River in Washington
Male Cinygma dimicki (Heptageniidae) (Western Light Cahill) Mayfly Spinner from the Cedar River in Washington
Ruler view of a Male Cinygma dimicki (Heptageniidae) (Western Light Cahill) Mayfly Spinner from the Cedar River in Washington The smallest ruler marks are 1 mm.
Male Cinygma dimicki (Heptageniidae) (Western Light Cahill) Mayfly Spinner from the Cedar River in Washington
Dorsal view of a Male Cinygma dimicki (Heptageniidae) (Western Light Cahill) Mayfly Spinner from the Cedar River in Washington
Ventral view of a Male Cinygma dimicki (Heptageniidae) (Western Light Cahill) Mayfly Spinner from the Cedar River in Washington
Male Cinygma dimicki (Heptageniidae) (Western Light Cahill) Mayfly Spinner from the Cedar River in Washington

This mayfly was collected from the Cedar River in Washington on July 2nd, 2021 and added to Troutnut.com by Troutnut on July 4th, 2021.


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Male Cinygma dimicki (Western Light Cahill) Mayfly Spinner Pictures

Collection details
Location: Cedar River, Washington
Date: July 2nd, 2021
Added to site: July 4th, 2021
Author: Troutnut
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