Header image
Enter a name
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 Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.
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 Genus Onocosmoecus (Great Late-Summer Sedges)

The most common species of this genus is Onocosmoecus unicolor.

Where & when

Time of year : Late summer and early fall

Preferred waters: Lakes and slow streams

This genus is nearly as large as Dicosmoecus, but not quite as impressive because its emergence is less concentrated. It can still produce fishable hatches, especially in lakes.

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

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

Genus Range

Larva & pupa biology

Diet: Mostly detritus

Current speed: Slow or still

Specimens of the Caddisfly Genus Onocosmoecus

2 Adults
1 Male Adult
3 Larvae

Start a Discussion of Onocosmoecus


  • LaFontaine, Gary. 1981. Caddisflies. The Lyons Press.

Caddisfly Genus Onocosmoecus (Great Late-Summer Sedges)

Species in Onocosmoecus
Onocosmoecus unicolor
Species in Onocosmoecus: Onocosmoecus unicolor
1 species (Onocosmoecus sequoiae) isn't included.
Genus Range
Troutnut.com is copyright © 2004-2024 (email Jason). privacy policy