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Trichoptera: Brachycentridae of Gunnison County, Colorado

Brachycentrus americanus
Log Cabin Casemakers, American grannom

(Banks) 1899
Updated 20 Feb 2024
TSN 116912
Brachycentrus americanus underwater population on a rock in the East River, Gunnison County, CO


These are stream and river insects. Larvae live in a tapered, four-sided (square) wooden case with a "log cabin" or transverse arrangement of twigs, pine needles and anything else useful in their habitat. Easily identifiable in the field or lab due to the distinctive case. The larvae are bright green when alive. The larvae fasten the front edge of their case to the substrate with silk and raise their second and third pair of legs in the current to filter food particles out of the water column.

Locations Collected

Common and widespread in this county, state and country as well as the entire nearctic and eastern palearctic. The Illinois Natural History Survey (INHS) Database shows this species is present "at Parlin", "South of Gunnison, near Cochetopa" and "the 1st bridge above Cow Creek Confluence". I have collected this species in Cement Creek, Coal Creek, East River meanders, East River near Crested Butte South, Slate River, Taylor River and the Gunnison River. While present in the upper East River Valley, it is less common in the steeper, faster flowing and turbulent streams.

Good Links

On this website:
Brachycentrus occidentalis

Outside Links:
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.


Allan,JD 1987 Macroinvertebrate drift in a Rocky Mountain stream. Hydrobiologia 144, 261-268.
     Working in Cement Creek in Gunnison County, Allan looked at aquatic insects drifting in the water column for 24 hour time periods during the summers of 1976 and 1977. On page 263, he briefly says "Trichoptera (mostly several species of Rhyacophila, but occasional Hydropsychidae and Brachycentrus americanus (Banks) always exhibited very low drift densities."

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 1899 Descriptions of new North American neuropteroid insects. Transactions of the American Entomological Society 25:199-218.
     Originally described as Oligoplectrum americanum.
Nathan Banks 1899 description of the new caddisfly species Oligoplectrum americanum, which is now called Brachycentrus americanus or the American Grammon

Blinn,DW and Ruiter,DE 2006 Tolerance values of stream caddisflies (Trichoptera) in the lower Colorado river basin, USA. The Southwestern Naturalist 51(3):326-337.
     Abstract: " One hundred and four caddisfly species within 42 genera and 17 families were collected from 93 stream sites in the xeric landscape of the lower Colorado River Basin, USA. Species richness showed a significant negative correlation with channel embeddedness. Forestland had higher species richness than grassland, desert, or urban caddisfly assemblages, and fewer caddisfly species occurred in the salt-cedar (Tamarix) than in willow-alder (Salix-Alnus) and cottonwood-sycamore (Populus-Plantanus) riparian communities. Hydroptilidae comprised nearly 35% of the average relative abundance of caddisflies and were generally tolerant of impaired stream environments. Hydroptila arctia composed the greatest relative proportion of species. Adjusted specific conductance and channel embeddedness metrics showed close agreement with published tolerance values for caddisfly species listed by the U.S. Environmental Protection Agency; genera were in less agreement. Amphicosmoecus canax, Brachycentrus americanus, Culoptila moselyi, Glossosoma ventrale, Ochrotrichia ildria, Psychoglypha schuhi, and Ylodes reuteri were most commonly associated with streams with low salinities and low embeddedness, whereas Cheumatopsyche enonis, Hydropsyche auricolor, Hydroptila ajax, Hydroptila arctia, Neotrichia okopa, Smicridea signata, and Smicridea fasciatella reached highest numeric importance in streams with high salinities and embeddedness. "

Canton,SP and Ward,JV 1981 The aquatic insects, with emphasis on Trichoptera, of a Colorado stream affected by coal strip-mine drainage. Southwestern Naturalist 25 4, 453-460.
     They studied Trout Creek where it runs through the Edna Coal Mine in northwestern Colorado. The mine spoils were 30 meters from the edge of the creek (approximately a 100 foot buffer zone). They found the aquatic insect density (numbers per square meter) and biomass (weight in grams per square meter) did not change above and below the mine. The Shannon-Weaver Diversity index also showed no difference between sites. However the community structure (which species were present and proportions) did change. Since there were irrigation water and cattle influences at their downstream site, their results may reflect these additional water uses. They note the biggest visible change at this mine is the loss of willow and alder trees downstream of the mine. The caddisfly population changed the most between sites, shifting from a mix of families above the mine to dominance by Hydropsychidae and Glossosomatidae below the mine.
B. americanus relative abundance did not change above and below the mine.

Brachycentrus americanus caddisfly population looking into the clear water of the East River in JUly of 2018 Clements,WH; Carlisle,DN; Lazorchak,JM; Johnson,PC 2000 Heavy metals structure benthic communities in Colorado mountain streams. Ecological Applications 10(2)626-638. Abstract
     Quote from page 633: "Rhyacophila sp.(Fig.5j) was the only caddisfly that showed a significant response to metal level and was lower at medium-metal sites. Differences among metal categories in abundance of the three other dominant caddisflies, (Brachycentrus americanus, Hydropsyche sp., and Lepidostoma sp.) and the blackfly Simulium sp. were not significant (Fig. 5g, h, i, k)."

Clubb,RW; Gaufin,AR; Lords,JL 1975 Acute cadmium toxicity studies upon nine species of aquatic insects. Environmental Research 9, 332-341.

Colburn,T (1982a) Aquatic insects as measures of trace element presence in water: Cadmium and Molybdenum. Aquatic Toxicology and Hazard Assessment: Fifth Conference, ASTM STP 766, J.G. Pearson, R.B. Foster, and W.E. Bishop, Eds., American Society for Testing and Materials, pgs 316-325.
     She discusses a taxa from Coal Creek called Brachycentrus brachycentrus. There are two species of Brachycentridae in Coal Creek, Brachycentrus americanus and Micrasema bactro. I assume she was working with B. americanus since it is in the right genus, is more common and bigger than Micrasema. She collected insects from what she thought was a reference or clean site up Coal Creek, however it was below Elk Creek. Elk Creek has a rather nasty mine called the Standard Mine up near the headwaters, this mine is now a Superfund site. So her bugs may have had some metal exposure before the experiment. Anyway, she found that both live and dead insects bioaccumulated Cadmium and Molybdenum after only a few days in the Slate River. Levels of both metals increased over time in the insects. Interestingly the water samples showed no Molybdenum present, indicating the insects were accumulating Molybdenum from the sediments or pulses of Mo in the water at times other than the water samples were taken.

Denning,DG 1983 New and interesting Trichoptera from the western United States. Pan-Pacific Entomologist 58, 206-215.
     Compares the adults of B. americanus and Brachycentrus occidentalis among other things.

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
     Has keys to adult males.

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

Gallepp,GW 1974 Diel periodicity in the behavior of the caddisfly, Brachycentrus americanus (Banks). Freshwater Biology 4, 193-204.
     Studied in an artificial stream and Lawrence creek in Wisconsin, B. americanus had a univoltine life cycle (one generation per year). Eggs were laid from mid June all summer. Larvae grew slower in the fall and winter, but faster in the spring. They pupated from May on and adults were present from June to September. B. americanus had 5 larvae instars with 2 sizes (sexual dimorphism) in the final instar. Females pupated in longer cases. Gallepp notes that B. americanus is usually an omnivorous, "sessile filter feeder". They attach the front of their case to the substrate and sit with their long middle and hind legs over their head in the current filtering food from the current with the bristles and spines on their legs. They tended to release large particles such as leaves, but brought smaller particles down to their mouth. Small objects were eaten with the shorter front legs (proleg) only. Other pieces of food were handled with all legs as needed.

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."

Gill,BA; Harrington,RA; Kondratieff,BC; Zamudio,KR; Poff,NL and Funk,WC 2014 Morphological taxonomy, DNA barcoding, and species diversity in southern Rocky Mountain headwater streams. Freshwater Science 33(1) 288-301.
     Working in wadeable streams on the Front Range of Colorado, they found a cryptic species of Brachycentrus along with B. americanus.

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.
     Working in the Flathead River of Montana, the authors found that B. americanus larvae hatched from eggs in the fall and overwintered as early instar larvae. They grew rapidly as water temperatures rose in the spring, but temporarily halted growth during spring runoff. B. americanus emerged as adults during August and September. They avoided competition with Brachycentrus occidentalis larvae by slightly staggered life cycles, with adults of B. occidentalis emerging after peak runoff in late June.

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

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 1606 to 3048m and adult collection dates are 17 April to 6 September. Quote from page 425: "Denning (1983) compared the male and female of this species with B. occidentalis Banks 1911 making future incorrect identifications of the two adults unlikely. Flint (1984) wrote keys to adult males and larvae for the species of Brachycentrus in North America. " They list this species as present in Gunnison county.

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

Johnson,KR; Jepson,PC; Jenkins,JJ 2008 Esfenvalerate-induced case-abandonment in the larvae of the caddisfly (Brachycentrus americanus). Environmental Toxicology and Chemistry 27(2) 397-403. Abstract">PDF
     Abstract: "Field-collected Brachycentrus americanus Banks (Trichoptera: Brachycentridae) larvae were used to investigate the relationship between esfenvalerate exposure and case-abandonment response, determine larval ability to construct a new case, and measure the change in predation risk to insects in rebuilt cases. We evaluated case-abandonment following four environmentally relevant esfenvalerate exposures, 0.05, 0.1, 0.2, and 0.4 µg/L; 48-h exposures to 0.2 and 0.4 µg/L (nominal) esfenvalerate both resulted in over 60% of larvae abandoning cases and were statistically indistinguishable. Propensity to engage in building behaviors was significantly diminished in 0.2 and 0.4 µg/L esfenvalerate-exposed insects that had abandoned cases, with less than 20% of exposed insects producing cases. Cases built by intoxicated larvae were characterized by a disorganized composition, and required half the pressure to crush versus cases built by nonexposed larvae. Pre-exposing case-building material to 1 µµg/L esfenvalerate also reduced the physical strength of rebuilt cases. Larvae inhabiting weaker rebuilt cases and larvae without cases were significantly more susceptible to predation by second year Hesperoperla pacifica Banks (Plecoptera: Perlidae) stonefly nymphs than those in original cases. Overall, we concluded that small behavioral responses can have profound consequences for survival of species and reveal susceptible stages in life-cycles that can be overlooked by conventional approaches to ecological risk assessment."

Kohler,SL and Hoiland,WK 2001 Population regulation in an aquatic insect: the role of disease Ecology 82(8) 2294-2305. Abstract and first page

Mangum,FA and Madrigal,JL 1999 Rotenone effects on aquatic macroinvertebrates of the Strawberry River, Utah: a five-year summary. Journal of Freshwater Ecology, 14(1), 125-135. PDF
     Abstract: " Before treatment with a 3 mg/1 Noxfish (0.15 mg/1 active ingredient; rotenone) for 48 hours, benthic invertebrate communities were quantitatively sampled with a modified Surber net. Then spring, summer, and fall post-rotenone samples were taken monthly at each of four Strawberry River stations for five years. Statistical analyses of the data indicated that the application of rotenone had a significant effect on the following species density: Cinygmula sp., Pteronarcella badia, Hesperoperla pacifica, Hydropsyche sp., and Brachycentrus americanus. Thirty-three percent of the benthic invertebrate taxa at the four stations showed resistance to rotenone. Up to 100% of Ephemeroptera, Plecoptera and Trichoptera species were missing after the second rotenone application. Forty-six percent of the taxa recovered within one year, but 21% of the taxa were still missing after five years. Of the 19 taxa still missing, 47% were Trichoptera, 21% were Ephemeroptera, 16% were Plecoptera, 11% were Coleoptera, and 5% were Megaloptera. "

Mecom, John O. 1972a Feeding habits of Trichoptera in a mountain stream. Oikos 23: 401-407. Abstract and first page
     Abstract: " The gut contents of more than 900 Trichoptera larvae from the St. Vrain River of Colorado were determined by Millipore filter analysis. They ingested a mixed diet of detritus, vascular plants, diatoms and other algae (e.g. Ulothrix). Vascular plant fragments, detritus, and filamentous algae were the major food categories ingested from late spring through early summer, while diatoms were most commonly consumed in mid-winter and early spring. Seasonal dietary changes were apparently related to general availability of organic material and larval microhabitat. Hydropsyche sp., Arctopsyche grandis, Hydropsyche occidentalis and Brachycentrus americanus were predatory or cannibalistic during a brief period from May to August. This carnivorous behavior was not directly correlated either to species crowding or population developmental changes. "

Mecom, John O. 1972b Productivity and distribution of Trichoptera larvae in a Colorado mountain stream. Hydrobiologia 40(2): 151 - 176. ISSN: 0018-8158 (Paper) 1573-5117 (Online) DOI: 10.1007/BF00016789 Abstract

Mecom,JO and Cummins,KW 1964 A preliminary study of the trophic relationships of the larvae of Brachycentrus americanus (Banks) (Trichoptera: Brachycentridae). Transactions of the American Microscopical Society 83: 233-243. PDF

Merrill,D 1969 The distribution of case recognition in ten families of caddis larvae (Trichoptera). Animal Behavior 17(3)486-493.

Palmquist,K; Jepson,P Jenkins,J 2008 Impact of aquatic insect life stage and emergence strategy on sensitivity to esfenvalerate exposure. Environmental Toxicology and Chemistry 27(8)1728-1734 Abstract

Rader,RB and Ward,JV 1988 Influence of regulation on environmental conditions and the macroinvertebrate community in the upper Colorado River. Regulated Rivers: Research and Management 2:597-618. PDF
     Quote from page 611 and 612: "The reference site was represented by twelve species of caddisflies, including relatively abundant populations of Arctopsyche grandis and Rhyacophila acropedes. Trichopterans at the regulated site, however, were represented by nine rare and three slightly more abundant caddisflies (Hydroptila sp., Brachycentrus americanus, and Hesperophylax designatus). The abundance of net-spinning caddisflies was significantly reduced in the regulated site compared to both reference and recovery locations (p=0.05), as has been reported by several workers (Armitage and Capper, 1976; Müller, 1962; Ward, 1987).
The thirteen species of Trichoptera in the recovery site included four of the most abundant species of macroinvertebrates at that site: Glossosoma ventrale, Brachycentrus americanus, Lepidostoma ormeum, Oligophlebodes minutes. Ward (1987) summarized the effects of regulation on Trichoptera in Rocky Mountain streams and concluded that Rhyacophila and Hydropsyche were the only genera commonly occurring at both regulated and reference locations, whereas Brachycentrus, Glossosoma, Arctopsyche, and Lepidostoma were often reduced or absent in regulated segments. With the exception of Brachycentrus americanus, which was significantly more abundant in the regulated and recovery sites, compared to the reference site (p=0.05), data from this study concur with previous conclusions concerning the influence of reguation on Trichoptera (Ward, 1987). "

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; 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 dam."

Ward,JV, Kondratieff,BC and Zuellig,RE 2002 An Illustrated Guide to the Mountain Stream Insects of Colorado. 2nd ed. University Press of Colorado, Boulder, Colorado. 219 pages.
     Has an illustration of B. americanus and its classic case on page 118

Wiggins,GB 1996 Larvae of the North American Caddisfly Genera (Trichoptera). 2nd Edition. University of Toronto Press, 457 pages.
     Has illustrations of the larvae and 4-sided case of B. americanus.

Brown, WS 2005 Caddisflies (Trichoptera) of Gunnison County, Colorado USA