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Trichoptera: Brachycentridae of Gunnison County, Colorado

Brachycentrus occidentalis
Early grannom, Mother's Day Caddis

Banks 1911
Updated 20 Feb 2024
TSN 116918

Good Links

On this website:
Brachycentrus americanus

Other Websites:
Photos, Map, Museum specimens, DNA - Barcodinglife.org

Arkansas River Hatch - from the Denver Post http://www.denverpost.com/news/ci_3700264

Yellowstone River Hatch - The Mother's Day Hatch http://www.yellowstoneflyfishing.com/caddisflies.htm
     After a good discussion of fishing and caddisfly hatches they talk about B. occidentalis partway down the page.

Illustration - University of Alberta Entomology Collection Species page
     Has illustration of male genitalia,description, habitat information, range and more.


Balistrieri,LS; Mebane,CA and Schmidt,TS 2020 Time-dependent accumulation of Cd, Co, Cu, Ni, and Zn in mayfly and caddisfly larvae in experimental streams: Metal sensitivity, uptake pathways, and mixture toxicity. Science of the Total Environment, 732. html

Banks,N 1911 Descriptions of new species of North American Neuropterid Insects. Transactions of American Entomological Society 37, 335-360.
     Describes this species on page 355, and illustrates it on plate 13 and figure 32.

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. 1984 The genus Brachycentrus in North America, with a proposed phylogeny of the genera of Brachycentridae (Trichoptera). Smithsonian Contributions to Zoology 398:1-58. PDF
     The author studied larval specimens from the Black Canyon of the Gunnison in Montrose County.

Flint,OS, Jr. 1984. On the genus Brachycentrus (abstract). Pages 143 in Proceedings of the 4th International Symposium on Trichoptera (J. C. Morse, ed.) Dr. W. Junk, The Hague.

Gallepp,GW 1974 Behavioral ecology of Brachycentrus occidentalis Banks during the pupation period. Ecology, Vol. 55(6) 1283-1294.
     Abstract: "The behavioral ecology of four populations of Brachycentrus occidentalis, maintained on different rations in four separate simulated stream channels, was followed daily from February to May as the larvae pupated and eclosed. Before pupation, the behavior of the population changed markedly as filtering decreased and larvae became unattached and laboratory drift increased. Cases of males were about 3 mm shorter than females. Median time within the pupal case of males and females was 34.5 and 31.0 days, respectively at 10°C. As pupation proceeded, larvae cannibalized pupae. Generally as feeding rate decreased, behavioral changes and pupation were delayed, cannibalism increased and percentage of females eclosing decreased. Females attempted cannibalism more often than males, and showed a higher percentage of successes. Of 160 pupal cases collected from Lawrence Creek, Wisconsin, approximately 9% showed evidence of cannibalism. An additional 32% were infested with Eukieffefriella sp., a small chironomid. Cannibals, predators, and parasites are considered as agents of selection pressure in connection with case construction and pupal distribution among the Trichoptera."

Gallepp,GW, Jr. 1975 The behavioural ecology of larval caddisflies, Brachycentrus americanus and Brachycentrus occidentalis. Dissertation Abstracts International 35: 4532.

Gallepp,G 1976 Temperature as a cue for the periodicity in feeding of Brachycentrus occidentalis (Insecta: Trichoptera). Animal Behaviour 24: 7-10.

Gallepp,GW 1977 Responses of caddisfly larvae (Brachycentrus spp.) to temperature, food availability and current velocity. American Midland Naturalist 98(1)59-84.
     Abstract: "Larvae of the stream caddisflies, Brachycentrus americanus and Brachycentrus occidentalis, were studied in eight simulated stream channels to determine their behavioral responses to temperature, food availability (brine shrimp) and current velocity. For both species, filtering, withdrawn and case-building were the primary behavior patterns of larvae that had attached their cases to the substrate. Most larvae not attached to the substrate were crawling or holding. As temperatures increased above 8 C, B. occidentalis larvae filtered more frequently; but above 20 C the percentage of larvae filtering steadily decreased and the percentage withdrawn increased dramatically with increasing temperature. Percentages of larvae case-building and unattached generally decreased over the range of 4 to 27 C. Despite this decrease in case-building, B. occidentalis larvae generally grew faster as temperature increased from 4-16 C. Behavior of B. americanus as a function of temperature was similar to behavior of B. occidentalis. Both species responded to decreased ration by increasing the percentage of time filtering. Although many larvae were unattached and probably grazing in Lawrence Creek, few larvae were unattached in the laboratory, even at the lowest ration (1.2% of the bodv weight per day). Growth and case-building activity of B. americanus larvae were directly related to ration. Over the range of current velocities of 7-26 cm/sec, behavior of B. occidentalis changed little. At 5 cm/sec fewer larvae filtered and more were unattached; this suggested a threshold response to current velocity. Increasing temperatures from 10-20 C caused the percentage withdrawn at low velocities to increase; however, this trend was hardly noticeable at velocities above 10 cm/sec. In these tests. Brachycentrus were more responsive to temperature and food availability than to current velocity. The interaction of temperature, food availability and current velocity largely controls the bioenergetic state of larvae and thus the behavior and ecology of Brachycentrus."

Gaufin,AR; Clubb,R and Newell,R 1974 Studies on the tolerance of aquatic insects to low oxygen concentrations. Great Basin Naturalist 34:45-59. PDF
      The authors studied the acute short term tolerance of aquatic insects to low oxygen. They used the 96 hour Median Tolerance Limit. They did not find a TLm96 for B. occidentalis. The authors had 90% survival from 2-4 mg/l oxygen with their experimental apparatus.

Gaufin,AR and Hern,S 1971 Laboratory studies on tolerance of aquatic insects to heated waters. Journal of the Kansas Entomological Society 44:240-245. PDF
     Abstract: "The mature larvae of fifteen species of aquatic insects (Diptera, Ephemeroptera, Plecoptera, and Trichoptera) and the scud (Amphipoda) were tested to determine their relative sensitivity to heated waters under laboratory conditions. The temperature at which 50% died after 96 hours (TLm96) was recorded as the lethal temperature. This ranged from 11.7 C for the torrential stream mayfly, Cinygmula par Baton, to 32.6 C for the snipefly, Atherix variegata Walker. "       The TLm96 for B. occidentalis was 29.7°C.

Hauer,FR; Stanford,JA 1986 Ecology and co-existence of two species of Brachycentrus (Trichoptera) in a Rocky Mountain River. Canadian Journal of Zoology 64 7, 1469-1474.

Herrmann,SJ; Ruiter,DE and Unzicker,JD 1986 Distribution and records of Colorado Trichoptera. Southwestern Naturalist 31 4, 421-457.
     They note the habitat for this species is streams and rivers, the altitudinal range is 1615 to 2926m and adult collection dates are 16 April to 6 July. Quote from page 425: "In Colorado this species is usually more common below 1829m while B. americanus more common above 1829m; B. occidentalis also seems to ewerge earlier." They list this species as present in Gunnison county.

Hauer,FR and Stanford,JA 1986 Ecology and co-existence of two species of Brachycentrus (Trichoptera) in a Rocky Mountain River. Canadian Journal of Zoology 64 7, 1469-1474.
     Studying the Flathead River of Montana for three years, the authors found that B. occidentalis larvae appeared as early instar larvae in mid to late summer and overwintered as 4th or 5th instar larvae. They were active until spring runoff and pupated in May and June. B. occidentalis emerged as adults during August and September. They avoided competition with Brachycentrus americanus larvae by slightly staggered life cycles, with adults of B. americanus emerging in late summer and early fall.

Hauer,FR; Stanford,JA and Ward,JV 1989 Serial discontinuities in a Rocky Mountain river. II. Distribution and abundance of Trichoptera. Regulated Rivers: Research and Management 3, 177-182.

Mebane,CA; Schmidt,TS; Miller,JL and Balistrieri,LS 2020 Bioaccumulation and toxicity of cadmium, copper, nickel, and zinc and their mixtures to aquatic insect communities. Environmental toxicology and chemistry, 39(4) 812-833. PDF

The United States Geological Survey (USGS) National Water Quality Assessment Data Warehouse (NAWQA) shows this species is present in Gunnison County. Data as of 1Sep2005

Voelz,NJ and Ward,JV 1996a Microdistributions, food resources and feeding habits of filter-feeding Trichoptera in the Upper Colorado River. Archiv fur Hydrobiologie 137 3, 325-348.

Voelz,NJ and Ward,JV 1996b Microdistributions of filter-feeding caddisflies (Insecta:Trichoptera) in a regulated Rocky Mountain river. Canadian Journal of Zoology 74, 654-666.

Voelz,NJ; Poff,NL and Ward,JV 1994 Differential effects of a brief thermal disturbance on caddisflies (Trichoptera) in a regulated river. American Midland Naturalist 132 1, 173-182.
     Abstract: " During studies on filter-feeding and grazing caddisflies in the regulated upper Colorado River, a problem developed with the deep-release mechanism of Granby Dam and water had to be released from the surface for 16 days in August 1986. Maximum water temperatures exceeded the normal summer maxima by at least 4-5 C for up to 12 km below the reservoir. Samples taken along the longitudinal profile below the reservoir showed that populations of several caddisflies species, which had been numerically abundant in previous years, were virtually eliminated after this period of increased water temperature. Some species experienced immediate reductions, presumably due to larval/pupal mortality (e.g., Brachycentrus americanus, Glossosoma ventrale, G. parvulum), while others exhibited lagged responses over the next several months, presumably due to reduced hatching success and extensive winter mortality (e.g., Glossosoma verdona). Interestingly, at some sites, B. americanus and other caddisfly species were largely unaffected by the elevated temperatures. Species showing the greatest resilience to the thermal disturbance were either those having abundant terrestrial adults present at the time (e.g., Agapetus boulderensis) or those potentially having broad thermal tolerances (e.g., Brachycentrus occidentalis). Most studies concerning the effects of extreme temperature change on lotic organisms have dealt with heated effluents or the general thermal impacts induced by river regulation. This is the first report, that we are aware of, detailing the potential effect of short-term elevated temperatures on lotic macroinvertebrates in a river regulated by a deep-release dani."

Wetmore,SH; Mackay,RJ and Newbury,RW 1990 Characterization of the hydraulic habitat of Brachycentrus occidentalis, a filter-feeding caddisfly. Journal of the North American Benthological Society 9: 157-169.
     Abstract: "Local velocity and flow profiles (50 cm in length) were measured in accelerating transitional-velocity zones in two 20-40-m long contrasting reaches of cobble and shale substrate in Wilson Creek, Manitoba, to characterize the observed hydraulic habitat of individual Brachycentrus occidentalis larvae (instars IV and V). Both instars in the cobble reach were in local habitats with faster water-column velocities, shallower depths, steeper water-surface slopes, and higher Froude numbers than randomly available locations in similar transitional-velocity zones. Values for hydraulic variables were mostly higher for instar IV habitat. Random conditions in the shale reach differed from those in the cobble reach, but differences between larval (instar V) habitat and random locations were again significant. Although larvae in the shale reach were at slower velocities and shallower depths than larvae in the cobble reach, they selected identical hydraulic regimes in terms of water-surface slope and Froude number. At both sites, Froude number was the best discriminator between larval and random locations. Microhabitats selected by B. occidentalis larvae coincided with zones of converging streamlines (average Froude number: 0.6) which may expose filter feeders to higher seston delivery rates. Additional observations for comparison showed that filter-feeding Simulium vittatum larvae selected positions with high Froude numbers also (average: 0.7), whereas Glossosoma intermedium larvae were in locations that differed from random only in depth. The profiling device used to map patches of local flow conditions allowed larval habitats to be distinguished from random locations within accelerating transitional-velocity zones, which are a subset of the full range of complex local flow zones in boulder-cobble stream beds."

Brown, WS 2005 Trichoptera of Gunnison County, Colorado, USA