Trichoptera: Limnephilidae of Gunnison County, Colorado
Onocosmoecus unicolor Banks 1897
Great Late-Summer Sedge
Updated 26 Aug 2020
On this website:
Introduction to the Limnephilidae
Photos, Map, Museum specimens, DNA - Barcodinglife.org
Illustration - University of Alberta Entomology Collection Species page
Has illustration of male genitalia, description, habitat information, range and more.
Banks,N 1897 New North american neuropteroid insects. Transactions of the American Entomological Society 24:21-31.
Described as Anabolia unicolor.
Djernæs,M and Sperling,FAH 2012 Exploring a key synapomorphy: correlations between structure and function in the sternum V glands of Trichoptera and Lepidoptera (Insecta). Biological Journal of the Linnean Society, 106: 561-579.
Flint,OS, Jr. 1960 Taxonomy and biology of Nearctic limnephilid larvae (Trichoptera), with special reference to species in eastern United States. Entomologica American 40:1-117.
Describes the larvae as Onocosmoecus quadrinatatus Banks.
Herrmann,SJ 1990 New record and range extension for Rhyacophila wallowa (Trichoptera: Rhyacophilidae) from Rocky Mountain National Park, Colorado. Entomological news (USA).
While studying R. wallowa, the author found O. unicolor adults near the cold streams Fall River and Chiquita Creek at 2640m or 8660ft amsl in Rocky Mountain National Park in Colorado.
Herrmann,SJ; Ruiter,DE and Unzicker,JD 1986 Distribution and records of Colorado Trichoptera. Southwestern Naturalist 31 4, 421-457.
The authors show this species present in Gunnison County.
Hoffmann, A and Resh, VH 2001 Oviposition site selection in four Trichoptera species - a hierachial spatial process. Presented at the NABS Annual meeting, La Crosse, Wisconsin. Abstract
Hoffmann,A; Resh,VH 2003 Oviposition in three species of limnephiloid caddisflies (Trichoptera): hierarchical influences on site selection. Freshwater Biology (48)6 1064-1077.
1. Oviposition site selection was studied in three trichopteran species; an undescribed species of Hydatophylax (Limnephilidae), Onocosmoecus unicolor (Limnephilidae) and Neophylax rickeri (Uenoidae), in two Coastal Range streams in California, U.S.A.
2. Hydatophylax sp. egg masses were generally found at or above the water surface on substrata near the bank in pools, where undercut banks, overhanging vegetation and rocks shaded attachment sites and provided wind protection. Onocosmoecus unicolor females deposited their egg masses exclusively above the water on moist emergent wood. The egg masses of N. rickeri were almost exclusively found in high velocity areas of riffles, where females oviposited under water and attached their egg masses to the submersed undersides of unembedded, protruding stones with large emergent surfaces.
3. For Hydatophylax sp. and N. rickeri, a hierarchical selection scheme is proposed in which females use cues at three different spatial levels (stream, stream subunit, substratum) to choose oviposition sites. Females of O. unicolor seemed to choose at only two different levels of spatial resolution (stream, substratum).
4. The formation of large aggregations of egg masses in N. rickeri and O. unicolor suggests that females actively choose oviposition sites where conspecific egg masses are already attached. The clustering of egg masses may minimise the risk of predation through the dilution effect, because egg masses of N. rickeri and O. unicolor are both attacked by dipteran predators.
5. Females of the three Trichoptera species studied are able to make a clear choice of oviposition site in the heterogeneous stream environment. In comparison with other stream microhabitats, these are characterised by stable and relatively predictable environmental conditions during the time of egg development, which is seen as the main selective pressure leading to the observed egg-laying behaviour. "
Irons,JG III 1988 Life history patterns and trophic ecology of Trichoptera in two Alaskan (U.S.A.) subarctic streams. Canadian Journal of Zoology, 66:1258-1265. Abstract
Kwong,L; Mendez,PK and Resh,VH 2011 Case-repair in 3 genera of caddisflies (Trichoptera) Proceedings of the 13th International Symposium on Trichoptera. Majecka,K; Majecki,J and Morse,J (Editors) Zoosymposia 5: 269-278 PDF
Lessard,JL; Merritt,RW and Cummins,KW 2003 Spring growth of caddisflies (Limnephilidae: Trichoptera) in response to marine-derived nutrients and food type in a Southeast Alaskan stream. International Journal of Limnology 39(1) 3 - 14. PDF
Abstract: "The short-term stimulation of production, due to marine-derived nutrients (MDN) from spawning salmon, is well documented for certain trophic levels in stream communities (e.g., algae and insect biomass). The effect of these nutrients on the stream ecosystem as a whole, however, remains unclear especially later in the year. Trichopterans have been shown to feed on salmon and other fish carcasses and there is evidence for greater growth rates in the presence of salmon tissue. To address the question of long-term MDN subsidy on trichopterans, we investigated the growth of three limnephilid caddisflies in the spring in the Harris River on Prince of Wales Island, Southeast Alaska. The Harris River has a natural waterfall barrier to salmon and receives large runs of pink (O. gorbuscha) and chum (O. keta) salmon each fall. We selected two shredding caddisflies (Onocosmoecus unicolor) and (Psychoglypha spp.) and one facultative scraper, (Dicosmoecus atripes) for our study. We had two objectives : 1) compare the spring growth of larval caddisflies in a stream section that receives a large autumn run of salmon with their growth in a stream section that is blocked from receiving salmon (due to an impassable waterfall), and 2) compare the growth of shredders with that of a facultative scraper when provided either leaves or biofilm on rocks as food.
Insects were placed in growth boxes in May 2001 with either conditioned alder leaves or stream rocks as food sources. The boxes were placed along with temperature loggers in both the salmon (below the waterfall) and non-salmon (above the waterfall) reaches. The boxes were removed 40 days later. In-stream samples were taken of each caddisfly initially and at the end of the experiment to establish in-stream growth versus growth in the boxes. All larvae were coaxed from their cases, measured for total wet length, dried and weighed. Only D. atripes and Psychoglypha spp. were growing during our experiment and both showed very high relative growth rates in the Harris River. Psychoglypha spp. and O. unicolor were both significantly larger in the leaf boxes and D. atripes was significantly larger in the rock boxes. Both D. atripes and Psychoglypha spp. had significantly greater relative growth rates between food types (on biofilm on rocks and leaves respectively). These results support the notion that D. atripes are most likely facultative scrapers at least in their first year of growth. None of these caddisflies showed differences in their final mean weights or relative growth rates between stream sections, suggesting no effect of MDN on their spring growth in the Harris River. Further research on caddisfly communities in the fall and winter will help clarify if MDN has an influence on the abundance and life history of these species closer to the salmon run. This study questions the long-term influence of MDN on stream communities, particularly those populations that do most of their production in the spring, months after salmon carcasses are no longer visible."
Wiggins,GB, and Richardson,JS 1987 Revision of the Onocosmoecus unicolor group (Trichoptera: Limnephilidae: Dicosmoecinae) . Psyche 93(3-4): 187-216. PDF
Wiggins,GB, and Richardson,JS 1989 Biosystematics of Eocosmoecus, a new Nearctic caddisfly genus (Trichoptera: Limnephilidae, Dicosmoecinae) Journal of the North American Benthological Society, 8(4) 355-369.
Abstract and first page
Quote from abstract: "Keys distinguishing Eocosmoecus, Onocosmoecus, and Dicosmoecus are given for adults, pupae, and larvae. "
Wisseman,RW 1987 Biology and distribution of the Dicosmoecinae (Trichoptera: Limnephilidae) in western North America. MS thesis Oregon State University PDF
Abstract: "Literature and museum records have been reviewed to provide a summary on the distribution, habitat associations and biology of six western North American Dicosmoecinae genera and the single eastern North American genus, Ironoquia. Results of this survey are presented and discussed for Allocosmoecus, Amphicosmoecus and Ecclisomyia. Field studies were conducted in western Oregon on the life-histories of four species, Dicosmoecus atripes, D. gilvipes, Onocosmoecus unicolor and Ecclisocosmoecus scylla. Although there are similarities between genera in the general habitat requirements, the differences or variability is such that we cannot generalize to a "typical" dicosmoecine life-history strategy. A common thread for the subfamily is the association with cool, montane streams. However, within this stream category habitat associations range from semi-aquatic, through first-order specialists, to river inhabitants. In feeding habits most species are omnivorous, but they range from being primarily detritivorous to algal grazers. The seasonal occurrence of the various life stages and voltinism patterns are also variable. Larvae show inter- and intraspecific segregation in the utilization of food resources and microhabitats in streams. Larval life-history patterns appear to be closely linked to seasonal regimes in stream discharge. A functional role for the various types of case architecture seen between and within species is examined. Manipulation of case architecture appears to enable efficient utilization of a changing seasonal pattern of microhabitats and food resources."