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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.

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington
This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.
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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Isogenoides hansoni (Appalachian Springfly) Stonefly Nymph Pictures

This large Perlodidae stonefly was a strikingly bright yellow color, more so than any other insect I've seen. I didn't enhance it much. See the discussion threads to follow how we identified this specimen, which was listed incorrectly for several years.

Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Ruler view of a Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York The smallest ruler marks are 1 mm.
Ventral view of a Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Dorsal view of a Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York
Isogenoides hansoni (Perlodidae) (Appalachian Springfly) Stonefly Nymph from Mongaup Creek in New York

This stonefly was collected from Mongaup Creek in New York on April 19th, 2006 and added to Troutnut.com by Troutnut on April 21st, 2006.

Discussions of this Nymph

Arcynopteryx
3 replies
Posted by Taxon on Jul 7, 2006
Last reply on Nov 9, 2011 by Entoman
Jason-

Not to despair; this is what American Stoneflies: A Photographic Guide to the Plecoptera by Bill P. Stark, Stanley W. Szezytko, and C. Ridley Nelson has to say about genus Arcynopteryx:

"This genus is represented in North America by A. compacta (McLachlan). This species ranges from Alaska to Maine and has been reported as far south as Colorado. Males usually have shortened wings and are easily recognized by the long, lash-like epiproct tip. Females and nymphs are quite similar to Skwala. A. compacta has been collected around alpine lakes in the northern Rocky Mountains. No photographs are available for this group."

Also, Arcynopteryx compacta is listed by Stark/Baumann as residing in New York.
I. hansoni
Posted by GONZO on Oct 3, 2010
Last reply on Oct 3, 2010 by GONZO
I believe that this is actually Isogenoides hansoni. When Dr. Chandler and Luke Myers made earlier "Cultus" comments on this specimen, they seem to have missed the prominent submental gills shown in photo #5 (and #7).

In addition to the submental gills (more than 2X as long as wide), the pale area on the 10th tergum, the distinct enclosed pale "M" mark on the head, and (often) the elongated pale spot in the center of the head are a few of the distinctive traits of this species. A complete description and a depiction of the dorsal habitus (figure #88) can be found in Sandberg and Stewart (Holomorphology and Systematics of the Stonefly Genus Isogeniodes, 2005).

The type specimens of I. hansoni were collected from my old homewaters on the Brodheads in 1937 by Preston Jennings (the author of the classic A Book of Trout Flies).

Cultus verticalis is a smaller, pale yellowish nymph, typically with a bolder, simpler dorsal pattern and less intricate markings on the dorsal surface of the head/thorax.
Anybody know the genus and species?
8 replies
Posted by Troutnut on Jul 7, 2006
Last reply on Feb 12, 2009 by Troutnut
This stonefly comes from a fertile, cold small stream in the Catskills. I tried to ID it using the key to genera in Merritt & Cummins but I ended up with a fairly confident identification that can't be correct: Arcynopteryx, a western mountain genus. So I'm stuck at couplet 89 in the M&C key.

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Isogenoides hansoni (Appalachian Springfly) Stonefly Nymph Pictures

Collection details
Location: Mongaup Creek, New York
Date: April 19th, 2006
Added to site: April 21st, 2006
Author: Troutnut
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