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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.

Case view of a Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington
It's only barely visible in one of my pictures, but I confirmed under the microscope that this one has a prosternal horn and the antennae are mid-way between the eyes and front of the head capsule.

I'm calling this one Pycnopsyche, but it's a bit perplexing. It seems to key definitively to at least Couplet 8 of the Key to Genera of Limnephilidae Larvae. That narrows it down to three genera, and the case seems wrong for the other two. The case looks right for Pycnopsyche, and it fits one of the key characteristics: "Abdominal sternum II without chloride epithelium and abdominal segment IX with only single seta on each side of dorsal sclerite." However, the characteristic "metanotal sa1 sclerites not fused, although often contiguous" does not seem to fit well. Those sclerites sure look fused to me, although I can make out a thin groove in the touching halves in the anterior half under the microscope. Perhaps this is a regional variation.

The only species of Pycnopsyche documented in Washington state is Pycnopsyche guttifera, and the colors and markings around the head of this specimen seem to match very well a specimen of that species from Massachusetts on Bugguide. So I am placing it in that species for now.

Whatever species this is, I photographed another specimen of seemingly the same species from the same spot a couple months later.
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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Golden Spinners

Like most common names,"Golden Spinner" can refer to more than one taxon. They're previewed below, along with 4 specimens. For more detail click through to the scientific names.

Mayfly Species Anthopotamus distinctus

These are sometimes called Golden Spinners.

Mayfly Species Cinygmula subaequalis

These are very rarely called Golden Spinners.
This is the only Eastern species of Cinygmula. It may produce fishable hatches in places but it is not a generally important mayfly.
Dorsal view of a Cinygmula subaequalis (Heptageniidae) (Small Gordon Quill) Mayfly Nymph from Mongaup Creek in New York
I had heard reports of a bright red heptageniid nymph before but never seen one until I found this early instar specimen in a very high water quality small stream in the Catskills.

Mayfly Species Ephemera varia

These are very rarely called Golden Spinners.
This is an excellent hatch of a different character than its Ephemera brethren. Rather than emerging in a flurry of activity within a week, the Ephemera varia hatch may last for more than a month in a single place.
Artistic view of a Female Ephemera varia (Ephemeridae) (Yellow Drake) Mayfly Dun from Aquarium in New York
This yellow drake dun hatched out of my aquarium over a month before her brethren in the wild are slated to emerge. She seems a bit small, and that might be the reason.
Lateral view of a Female Ephemera varia (Ephemeridae) (Yellow Drake) Mayfly Spinner from Cayuta Creek in New York
I found this female spinner ovipositing in a small stream. She came along while I was playing a trout -- every good bug seemed to do that last night! I didn't have my bug net, so I caught the trout in my landing net, released the trout, and caught the mayfly in my landing net. Her wing got a bit messed up from that.
A burrowing mayfly nymph. The juvenile stage of the brown drake, Ephemera simulans

Dorsal view of a Ephemera varia (Ephemeridae) (Yellow Drake) Mayfly Nymph from Fall Creek in New York
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