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Caddisfly Species Onocosmoecus unicolor (Great Late-Summer Sedge)

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Where & When


Regions: East, Midwest, West

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.


Pictures of 4 Caddisfly Specimens in the Species Onocosmoecus unicolor:

Specimen Page:12
Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly LarvaOnocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly Larva View 3 Pictures
Collected March 1, 2004 from unknown in Wisconsin
Added to Troutnut.com by Troutnut on January 25, 2006
Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly AdultOnocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly Adult View 2 Pictures
Collected October 5, 2011 from the Touchet River in Washington
Added to Troutnut.com by Bnewell on October 11, 2011
Male Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly AdultMale Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly Adult View 15 PicturesI 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 (Mesopleuron: The side of the insect mesothorax, and the part to which the fore wings are attached in mayflies.), which rules out Dicosmoecus. The midtibiae have 2 apical (Apical: Close to the apex; tip or end.) spurs and 1 pre-apical (Apical: Close to the apex; tip or end.) 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 to Troutnut.com by Troutnut on September 19, 2020
Specimen Page:12

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