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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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Case view of a Lepidostoma (Lepidostomatidae) (Little Brown Sedge) Caddisfly Larva from Mongaup Creek in New York
This one got a little bit damaged in the abdomen when I extracted it from its case. That's a delicate job.
Taxon
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Site Editor
Plano, TX

Posts: 1311
Taxon on May 18, 2007May 18th, 2007, 10:04 am EDT
Based on the case, I would think Platycentropus. Can you see if it has prosternal horns extending beyond the head capsule to mentum of labium? See Merrit p. 375 Figure 18.191.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Troutnut
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Bellevue, WA

Posts: 2758
Troutnut on May 18, 2007May 18th, 2007, 11:25 am EDT
It doesn't. The prosternal horns only reach to the back of the head. It took about 10 minutes screwing around under a microscope to even see the prosternal horns (the whole thing is about half a centimeter long and the legs really wanted to be in the way). But I finally got a good view, and they are short, so that rules ot Platycentropus. The case seemed like a good match, though.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

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