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.

This view of the pipeline, the Atigun River, and an impressive sunset/rise was one of my first views of the North Slope as I came through Atigun Pass in the middle of the night.

From the Atigun River in Alaska

Stream photos

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Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva

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.

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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.

Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Anybody know more about Maccaffertium terminatum?

This topic is about the Mayfly Species Stenonema terminatum

I have found no information about this species in angling literature, but one mediocre evening on the West Branch of the Delaware I found them to be a substantial part of the mixed bag of cahills and other mayflies causing a half-hearted rise of trout.

Example specimens

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Male Stenonema terminatum Mayfly Spinner

Male Stenonema terminatum (Heptageniidae) Mayfly Spinner from the Teal River in Wisconsin

2
Female Stenonema terminatum Mayfly Dun

Female Stenonema terminatum (Heptageniidae) Mayfly Dun from the Flathead River-Lower in Montana

1
Stenonema terminatum Mayfly Nymph

Stenonema terminatum (Heptageniidae) Mayfly Nymph from the Flathead River-lower in Montana

This is a subspecies M. terminatum terminatum, formerly called Stenonema. Found mostly in larger rivers in western Montana. This is an immature nymph.

Troutnut

Administrator
Bellevue, WA

Posts: 2758

Troutnut on Jun 8, 2007June 8th, 2007, 11:53 am EDT

I just wrote up what I found on the page for this species. I was mildly surprised to see so many of a species I've never seen mentioned in an angling context -- at least a few dozen throughout the evening. They piqued my curiosity.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

Konchu

Site Editor
Indiana

Posts: 498

Konchu on Jun 9, 2007June 9th, 2007, 2:05 am EDT

What more do ya wanna know?

Troutnut

Administrator
Bellevue, WA

Posts: 2758

Troutnut on Jun 9, 2007June 9th, 2007, 4:20 am EDT

Hatch timing, habitat preference, quirky behavior... anything relevant to fishing that might be associated with this species.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

Konchu

Site Editor
Indiana

Posts: 498

Konchu on Jun 11, 2007June 11th, 2007, 2:39 pm EDT

Larvae found on debris, rocks and aquatic vegetation in medium to large streams. Coarse sand/gravel substrate.

Spinners and duns are out around June-July in the Northeast and for a longer period (May-Aug) in the central and southern parts of its range.

Most of this was gleaned from:
Bednarik AF, McCafferty WP. 1979. Biosystematic revision of the genus Stenonema (Ephemeroptera: Heptageniidae). Can. Bull. Fish. Aquat. Sci. 201: 73 pp.

PS. This species was classified in the genus Stenonema until relatively recently.