Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York

Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

I like this one. Glacial river, taiga, tundra, and the perpetual ice cover of a massive high ridge dozens of miles away in the Wrangell Mountains.

From the Copper River in Alaska

Stream photos

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Female Sweltsa borealis (Boreal Sallfly) Stonefly Adult Female Sweltsa borealis (Boreal Sallfly) Stonefly Adult

Lateral view of a Female Sweltsa borealis (Chloroperlidae) (Boreal Sallfly) Stonefly Adult from Harris Creek in Washington

I was not fishing, but happened to be at an unrelated social event on a hill above this tiny creek (which I never even saw) when this stonefly flew by me. I assume it came from there. Some key characteristics are tricky to follow, but process of elimination ultimately led me to Sweltsa borealis. It is reassuringly similar to this specimen posted by Bob Newell years ago. It is also so strikingly similar to this nymph from the same river system that I'm comfortable identifying that nymph from this adult. I was especially pleased with the closeup photo of four mites parasitizing 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

9
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.