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.

Stream photos

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Female Hydropsyche (Spotted Sedge) Caddisfly Adult Female Hydropsyche (Spotted Sedge) Caddisfly Adult

Lateral view of a Female Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Adult from the Columbia River in Washington

7 Recently Added Photos

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.

Caddisfly Species Onocosmoecus unicolor (Great Late-Summer Sedges)

Where & when

Time of year : Mid-August to late October

Preferred waters: Rivers and lakes

This species is common in the Northwest and present but uncommon in the East.

In 83 records from GBIF, adults of this species have mostly been collected during August (35%), July (25%), September (22%), and October (11%).

In 55 records from GBIF, this species has been collected at elevations ranging from 16 to 10840 ft, with an average (median) of 5092 ft.

Species Range

source

Map of specific collection sites

Specimens of the Caddisfly Species Onocosmoecus unicolor

2 Adults

Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly Adult

11 Pictures

Lateral view of a Onocosmoecus unicolor (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Adult from Trealtor Creek in Idaho

One key characteristic not clearly photographed, but clear in under the microscope: this specimen's midtibiae have 2 apical spurs and 1 preapical spur.

Collected August 3, 2020 from Trealtor Creek in Idaho

Added by Troutnut on August 20, 2020

Collected August 3, 2020 from Trealtor Creek in Idaho and added by Troutnut on August 20, 2020

Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly Adult

2 Pictures

Onocosmoecus unicolor (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Adult from the Touchet River in Washington

Collected October 4, 2011 from the Touchet River in Washington

Added by Bnewell on October 11, 2011

Collected October 4, 2011 from the Touchet River in Washington and added by Bnewell on October 11, 2011

1 Male Adult

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

15 Pictures

Lateral view of a Male Onocosmoecus unicolor (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Adult from the Yakima River in Washington

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 16, 2020 from the Yakima River in Washington

Added by Troutnut on September 18, 2020

Collected September 16, 2020 from the Yakima River in Washington and added by Troutnut on September 18, 2020