Bionomics of dicosmoecus gilvipes (Trichoptera: Limnephilidae) in a large western Montane river [McCloud River, California]

• Published in: The American midland naturalist Vol. 108; no. 1; pp. 81 - 87
• Main Authors: Hauer, F. Richard, Stanford, Jack A.
• Format: Journal Article
• Language: English
• Published: University of Notre Dame 01-01-1982
• Subjects: Autumn; Diapause; Dicosmoecus gilvipes; Ecology; Freshwater; Freshwater ecology; Instars; Larvae; Larval development; Limnephilidae; Streams; Summer; Winter; USA, Montana, Flathead R
• ISSN: 0003-0031; 1938-4238
• DOI: 10.2307/2425295

Dicosmoecus gilvipes (Hagen) had a 2-year life cycle in the upper Flathead River, Montana. First-instar larvae appeared in spring and grew to fourth instar by late summer. Larvae typically entered fifth instar during late summer or autumn and spent the winter months attached to the undersides of large rocks in apparent diapause. Fifth-instar larvae were again active as water temperatures warmed above 1 C in March. In midsummer, fifth-instar larvae again attached their cases to the undersides of rocks and entered a 4- to 6-week prepupal diapause prior to metamorphosis. Adults emerged from late August through October. Early-instar larvae occurred primarily in depositional areas at the edge of riffles or in pools and backwater areas. Late-instar larvae were most frequently observed on and within the rubble substrate of lotic erosional zones, yet outside turbulent riffles. The change in habitat from depositional to erosional zones was coincident with decreased river discharge. The 2-year life cycle is explained in terms of temperature and food quantity-quality relationships.