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.

Stream photos

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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.

mean one thing, write another?

Male Onocosmoecus unicolor Caddisfly Adult

15 Pictures

Male Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly Adult

I first just assumed this was Dicosmoecus based on anglers' conventional wisdom since it's a large orange "October caddis," but Creno set me straight. I should have keyed it out. After another look under the microscope, it lacks an anepisternal wart on the mesopleuron, which rules out Dicosmoecus. The midtibiae have 2 apical spurs and 1 pre-apical spur, and from there the color pattern of the wing points to Onocosmoecus. The location then narrows the species to unicolor.

Collected September 17, 2020 from the Yakima River in Washington

Added by Troutnut on September 19, 2020

Creno
Grants Pass, OR

Posts: 302

Creno on Sep 19, 2020September 19th, 2020, 1:19 pm

Onocosmoecus unicolor?

Troutnut

Administrator
Bellevue, WA

Posts: 2752

Troutnut on Sep 19, 2020September 19th, 2020, 2:19 pm

Didn't mean one thing and write another -- you caught me assuming the genus based on angler-entomology instead of keying it out. Oops! After closer inspection under the microscope, of course you're right.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

Creno
Grants Pass, OR

Posts: 302

Creno on Sep 20, 2020September 20th, 2020, 11:19 am

Interesting that the western angling lit has Dicosmoecus as orange. Within the Dicosmoecinae only Onocosmoecus is orange, the rest are dark greys to blacks when alive and, like Onocosmoecus, often faded to browns when pinned. Amphicosmoecus could be considered orangish on some speciemens but the wings are typically more grey/brown with a reddish tint, and finely speckled. Onocosmoecus unicolor is one of those very widespread species that further study will likely reveal are comprised of several species. But not to worry, it probably won't happen soon :-) I forgot to mention - thanks for the great pics.