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Susan’s Purse-Making Caddisfly

Ochrotrichia susanae
U.S. State

Susan’s purse-making caddisfly (Ochrotrichia susanae) is a small caddisfly with dark brown wings crossed by three silver bands, with a wingspan of 2 mm. The larvae are aquatic and inhabit small, cold streams that are well-oxygenated, highly buffered, and low in trace metals. Susan’s purse-making caddisfly was identified as a new species in 1976, and has only been found in two sites in central Colorado: Trout Creek Spring in Chaffee County, where the species was first described, and High Creek Fen in Park County. This species is seriously threatened by habitat loss, primarily due to the effects of livestock grazing and timbering projects in the Trout Creek Spring area. The limited habitat of Susan’s purse-making caddisfly is also threatened by groundwater depletion due to increasing usage by surrounding cities, damage from unregulated off-road recreational vehicle use and hiking, and the effects of drought, altered stream hydrology, and changing water temperature that are likely to occur in the mountainous West due to global climate change.

The taxonomy of Susan’s purse-making caddisfly (O. susanae) is uncontested. Ochrotrichia susanae is a small caddisfly in the family Hydroptilidae (purse-maker or micro-caddisflies). It was first described by Flint and Herrmann (1976) from specimens taken in 1974 at Trout Creek in Chaffee County, Colorado. The genus Ochrotrichia is widespread and fairly diverse in North America, with over 50 species described species (Wiggins, 1996). Adults can be distinguished from other species in the genus Ochrotrichia based on characteristics of the genitalia.


Susan’s purse-making caddisfly (O. susanae) is a small hairy brown caddisfly (Flint & Herrmann, 1976). Adult forewings are 2 mm (0.078 inch) in length, and are dark brown with three transverse silver bands: one each at the wing base, the wing midline, and the wing apex.

Larvae in this family are very small (1-4 mm; 0.039-0.157 inch) and are free-living for the first four instars. The head and the dorsal surface (top) of all three thoracic segments are dark brown and sclerotized (hardened). When the larvae molt to the fifth instar, they develop enlarged abdomens, build purse-shaped cases from silk and sand, and become less active (Wiggins, 1996). Larval cases are small, flattened, bivalved, and open at each end, similar to other members of the genus Ochrotrichia. However, O. susanae larval cases are slightly shorter proportionally and are made from smaller grains of sand (Flint & Herrmann, 1976).

Life History

Feeding behavior of O. susanae larvae has not been observed directly, but larvae in this genus generally feed by scraping diatoms from rocks (Wiggins, 1996). Rocks in Trout Creek Spring that were thickly covered with larval cases were also associated with heavy growths of filamentous algae and moss.

Adult Trichoptera have reduced mouthparts and lack mandibles, but can ingest liquids.

Life Cycle
The larvae of Hydroptilidae are unusual among the case-making families of Trichoptera in that they are free-living until the final (fifth) larval instar, and then they construct a case which can be portable or cemented to the substrate (Wiggins, 1996). The larvae eventually pupate within this case. The adult flight period was estimated to be from late June to early August by Flint & Herrmann (1976), although adults were collected from mid-April to late July in a later survey (Herrmann et al., 1986). Susan’s purse-making caddisfly is thought to be univoltine, producing one generation per year.


Historic Distribution
The range and abundance of Susan’s purse-making caddisfly is not known prior to 1974, when the first specimens were collected and identified as a new species. The type locality for this species is Trout Creek Spring, which is located at an elevation of about 2750 m (9020 ft). Larvae, pupae, and adults were collected at the spring outfall area and as far downstream as ~130 m (426 ft).

Current Distribution
Susan’s purse-making caddisfly is known only from two sites in central Colorado: the type locality at Trout Creek Spring in Chaffee County, and High Creek Fen in Park County. A state-wide survey undertaken to provide distributional data for all Trichoptera in Colorado indicated that Susan’s purse-making caddisfly was present only at the type locality, Trout Creek Spring (Herrmann et al., 1986). The only other reported collection site for this species is the High Creek Fen area, about 20 miles north of the type locality (Durfee & Polonsky, 1995). High Creek Fen is a unique groundwater-fed wetland with high ecological diversity; it is considered a rare type of habitat, and the southernmost example of this type of ecosystem in North America (Cooper, 1996; Rocchio, 2005; Legg, 2007).

The USDA Forest Service Region 2 Sensitive Species Evaluation form (USDA Forest Service, 2007a) states: “Extensive field surveys have been conducted for the species (Herrmann et al., 1986). Over the past 30 years, even with extensive field work, only 2 populations have been found and the likelihood of major new populations is unlikely.”

Habitat Associations

Physical and chemical conditions of the type locality spring were assessed when Susan’s purse-making caddisfly was first collected and described (Flint & Herrmann, 1976). The results suggested that this species has a relatively narrow set of ecological requirements. Water temperatures in the spring habitat were cold and varied little (14.4–15.8°C). Stream conditions included extremely high levels of dissolved oxygen (at or near 100% saturation), as well as high concentrations of dissolved Ca, Mg, and SO4, which gave the water a higher conductance value than typically seen in most regional streams at the same elevation. Overall, larvae may be said to inhabit waters in small streams that are cold, well-oxygenated, highly buffered, and low in trace metals. Larvae and pupae were collected primarily from the sides of rocks in both the spring outfall and the downstream locations, especially in areas directly below small waterfalls in the creek, often clustered in clumps that covered the rocks. Like most caddisflies, the adults are weak fliers, flying only about 1-2 m when disturbed, and tend to remain close to the larval habitat for mating and oviposition.

Conservation Status

Susan’s purse-making caddisfly is a Region 2 Sensitive Species in Colorado (USDA Forest Service, 2007a). It was designated as a conservation target in a Nature Conservancy ecoregional assessment of the Southern Rocky Mountains ecoregion (The Nature Conservancy, 2001). Susan’s purse-making caddisfly has a Global Heritage Status Rank of G2. The United States National Heritage Status Rank is N2.


The primary threats to the survival of Susan’s purse-making caddisfly are impairment and destruction of their restricted habitat due to the effects of livestock grazing and logging-related activities.

The Trout Creek Spring area will be impacted by a proposed rangeland allotment plan for livestock grazing (USDA Forest Service, 2007c). The plan addresses allotment areas in the Salida, Leadville, and South Park areas, and encompasses a total of 340,000 acres, about half of which has suitable and accessible forage. Trout Creek Spring is located at the south end of the Lower Chubb allotment unit. Only one portion of this allotment, the Upper Chubb unit, has been designated as a benchmark area for meeting desired conditions. Current assessment of this benchmark area indicates that it is “moving towards”desired conditions, but has poor vegetation cover, composition, and structure in stream riparian areas on State-owned land in the allotment, large areas of bare ground and poor vegetation cover in grasslands and uplands of State- and federal-owned lands, reduced vigor in upland grasses, and willow die-off in riparian areas. A soil survey of the project area conducted in 1995 indicated that 20% of the Chubb allotment is considered to have severe or moderate erosion hazard potential.

The area is also subject to a new project called the North Trout Creek Hazardous Fuels Project (USDA Forest Service, 2007b), which will treat approximately 8,700 acres with salvage logging, thinning, and prescribed fire to reduce hazardous fuel loads.

Although both of these projects occur in the area surrounding the Trout Creek Spring type locality, and Susan’s purse-making caddisfly is listed as a Forest Service Region 2 Sensitive Species, the potential impacts of these activities on Susan’s purse-making caddisfly were not considered in either of the project environmental assessments and no surveys were conducted.

Additional threats to O. susanae include: livestock grazing, logging-related activities, roads, prescribed fire, de-watering of spring habitats, camping/hiking, ORV use in non-designated areas, small population size and stochastic events and global climate change.

Conservation Needs

See above.


Abdel-Magid, A. H, Trlica, M. J., and Hart, R. H. 1987. Soil and vegetation responses to simulated trampling. Journal of Range Management 40: 303-306.

Agouridis, C. T., Workman, S. R., Warner, R. C., and Jennings, G. D. 2005. Livestock grazing management impacts on stream water quality: a review. Journal of the American Water Resources Association. 41 (3): 591-606.

Anderson, P. G. 1996. Sediment generation from forestry operations and associated effects on aquatic ecosystems. Proceedings of the Forest-Fish Conference: Land Management Practices Affecting Aquatic Ecosystems, Calgary, Alberta.

Anderson, B. and Potts, D. F. 1987. Suspended sediment and turbidity following road construction and logging in western Montana. Journal of the American Water Resources Association 23 (4): 681–690.Angermeier P. L., Wheeler, A. P., and Rosenberger, A. E. 2004. A conceptual framework for assessing impacts of roads on aquatic biota. Fisheries 29 (12): 19-29.

Belsky A. J., Matzke, A., and Uselman, S. 1999. Survey of livestock influences on stream and riparian ecosystems in the western United States. Journal of Soil and Water Conservation 54 (1): 419-431.

Bowker, J.M., English, D.B.K., and Cordell, H.K. 1999. Projections of outdoor recreation participation to 2050. In: Outdoor recreation in American life: a national assessment of demand and supply trends (Cordell, H.K., Betz, C.J., Bowker, C.J., eds.). Sagamore Publishing, Champaign, IL. 449 pp. Available online.

Braccia, A. and Voshell Jr., J. R. 2007. Benthic macroinvertebrate responses to increasing levels of cattle grazing in Blue Ridge Mountain streams, Virginia, USA. Environmental Monitoring and Assessment 131:185–200.Cederholm, C.J., L.M. Reid, and E.O. Salo. 1981. Cumulative effects of logging road sediment on salmonid populations in the Clearwater River, Jefferson County, Washington. In: Washington Water Research Council. Proceedings from the conference on salmon-spawning gravel: a renewable resource in the Pacific Northwest. Washington State University, Washington Water Research Centre, Report 39, Pullman. Chaffee County Comprehensive Plan. 2000. Consensus Planning Inc., 99 pp. Available online.

Chaney, E., Elmore, W., and Platts, W. S. 1993. Managing change: livestock grazing on western riparian areas. Produced for U. S. Environmental Protection Agency by the Northwest Resource Information Center, Inc., Eagle, Idaho. 31 pp.

Clary, W. P. and Webster, B. F. 1989. Managing grazing of riparian areas in the intermountain region. General Technical Report INT-263. United States Department of Agriculture, Forest Service, Intermountain Research Station, Ogden UT. 15 pp.

Coles-Ritchie M. C., Roberts, D. W., Kershner, J. L., and Henderson, R. C. 2007. Use of a wetland index to evaluate changes in riparian vegetation after livestock exclusion. Journal of the American Water Resources Association 43 (3): 731-743. Colorado Department of Public Health and Environment. 2006. Status of Water Quality in Colorado –2006: The Update to the 2002 and 2004 305(b) Reports, Appendix D: 2006 303(d) List and Monitoring and Evaluation List. Colorado Department of Public Health and Environment, Water Quality Control Division.

Colorado Division of Wildlife. 2007. Colorado State Trust Lands. Colorado Division of Wildlife, Denver CO. Cooper D. J. 1996. Water and soil chemistry, floristics, and phytosociology of the extreme rich High Creek fen, in South Park, Colorado, U.S.A. Canadian Journal of Botany 74 (11): 1801-1811.

Cordell, H. K., McDonald, B. L., Teasley, R. J., Bergstrom, J. C., Martin, J., Bason, J., and Leeworthy, V. R. 1996. Outdoor recreation participation trends. In: Outdoor recreation in American life: a national assessment of demand and supply trends (Cordell, H.K., Betz, C.J., Bowker, C.J., eds.). Sagamore Publishing, Champaign, IL. 449 pp. Available online.

Dewson, Z. S., James, A. B. W., and Death, R. G. 2007. A review of the consequences of decreased flow for instream habitat and macroinvertebrates. Journal of the North American Benthological Society 26 (3):401–415.Durfee, R.S. and A.P. Polonsky. 1995. Inventory of aquatic and semiaquatic macroinvertebrates of High Creek Fen Preserve, Park County, Colorado: refugium for northern disjunct species. Unpublished report to The Nature Conservancy, Boulder, Colorado.

Erman, N. A. 2002. Lessons from a long-term study of springs and spring invertebrates (Sierra Nevada, California, U.S.A.) and implications for conservation and management. Conference Proceedings. Spring-Fed Wetlands: Important Scientific and Cultural Resources of the Intermountain Region, 2002. Available online.

Field, C.B., Mortsch, L.D., Brklacich, M., Forbes, D.L., Kovacs, P., Patz, J.A., Running, S.W. and Scott, M.J. 2007. Chapter 14: North America. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Parry, M.L., Canziani, O.F., Palutikof, J.P., van der Linden, P.J. and Hanson, C.E., eds.). Cambridge University Press, Cambridge, UK. Available online.

Fleischner, T. L. 1994. Ecological costs of livestock grazing in western North America. Conservation Biology 8 (3): 629-644.

Flint, O. S., and Herrmann, S. J. 1976. The description of, and environmental characterization for, a new species of Ochrotrichia from Colorado. Annals of the Entomological Society of America 69 (5): 894-898.

Forman, R. T. T. and Alexander, L. E. 1998. Roads and their major ecological effects. Annual Review of Ecology and Systematics 29: 207-231.

Furniss, M.J., Roelofs, T.D. and Yee, C.S. 1991. Road construction and maintenance. In: Meehan, W.R. (ed.) Influences of forest and rangeland management on salmonid fishes and their habitats. American Fisheries Society Special Publication 19.

Garber-Yonts, B. E. 2005. Conceptualizing and measuring demand for recreation on national forests: a review and synthesis. General Technical Report PNW-GTR-645. U.S. Department of Agriculture Forest Service, Pacific Northwest Research Station, Portland, OR. 40 pp. Available online.

Gillen, R. L., Krueger, W. C., and Miller, R. F. 1984. Cattle distribution on a mountain rangeland in northeastern Oregon. Journal of Range Management 37: 549-553.

Grace, J. M., III. 2002. Sediment movement from forest road systems-roads: a major contributor to erosion and stream sedimentation. American Society of Agricultural Engineers, December 2002, pp. 13-14.

Gucinski, H., Furniss,M. J., Ziemer, R. R. and Brookes, M. H. 2001. Forest roads: a synthesis of scientific information. General Technical Report PNW-GTR-509, United States Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland Oregon. Available online.

Herrmann, S. J., Ruiter, D. E., and Unzicker, J. D. 1986. Distribution and records of Colorado Trichoptera. The Southwestern Naturalist 31 (4): 421-457.

Holland, K. A., Leininger, W. A., and Trlica, M. J. 2005. Grazing history affects willow communities in a montane riparian ecosystem. Rangeland Ecology & Management 58 (2): 148-154.

Intergovernmental Panel on Climate Change. 2007. Summary for Policymakers. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Parry, M.L., Canziani, O.F., Palutikof, J.P., van der Linden, P.J. and Hanson, C.E., eds.). Cambridge University Press, Cambridge, UK. Available online.

Jones, J. A., Swanson, F. J., Wemple, B. C., and Snyder, K. U. 1999. Effects of roads on hydrology, geomorphology, and disturbance patches in stream networks. Conservation Biology 14 (1): 76-85. Kennedy, C. 1977. Wildlife conflicts in riparian management: water. In: Symposium on importance, preservation, and management of riparian habitat. U.S. Forest Service General Technical Report RM-43, Ft. Collins, CO.

Kovalchik, B.L. and W. Elmore. 1992. Effects of cattle grazing systems on willow dominated plant associations in central Oregon, In : Proceedings of a symposium on ecology and management of riparian shrub communities (Clary, W.P., McArthur, E.D., Bedunah, D. and Wambolt, C.L., eds.). USDA Forest Service General Technical Report INT-289. Ogden, UT.

Legg, T. M. 2007. Methods for identifying groundwater sources to High Creek Fen, South Park, Colorado. Geological Society of America, Annual Meeting, October 28-31 2007. Geological Society of America Abstracts with Programs, 39 (6): 475.

Leonard, S. G., Elsbernd, V., Borman, M., Swanson S., and Kinch, G. 1997. Grazing management for riparian-wetland areas. Bureau of Land Management Technical Report 1737-14. U. S. Department of the Interior, Bureau of Land Management, National Applied Resource Sciences Center. 63 pp.

Mathews, B. W., Sollenberger, L. E., Nair, V. D., and Staples, C. R. 1994. Impact of grazing management on soil nitrogen, phosphorus, potassium, and sulfur distribution. Journal of Environmental Quality 23 (5): 1006-1013.

McIver, J. D. and McInnis, M. L. 2007. Cattle grazing effects on macroinvertebrates in an Oregon mountain stream. Rangeland Ecology and Management 60: 293–303.Megahan, W.F. and Kidd, W.J. 1972. Effects of logging roads on sediment production rates in the Idaho Batholith. U.S. Forest Service Research Paper INT-123.

Merritt, R. W., K. W. Cummins, and M. B. Berg (eds). 2008. An introduction to the aquatic insects of North America. 4th edition. Kendall/Hunt Publishing Company, Dubuque, Iowa.1158 pp.

Miller, L.D., and Ortiz, R.F. 2007. Ground-water quality and potential effects of individual sewage disposal system effluent on ground-water quality in Park County, Colorado, 2001–2004. U.S. Geological Survey Scientific Investigations Report 2007–5220, 48 p.The Nature Conservancy. 2001. Southern Rocky Mountains: an ecoregional assessment and conservation blueprint. Available online.

Neary, D. G., Ryan, K. C., DeBano, L. F. (eds). 2005. Wildland fire in ecosystems: effects of fire on soils and water. General Technical Report RMRS-GTR-42-vol.4. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Ogden UT.

Orodho, A. B., Trlica, M. J., and Bonham, C. D. 1990. Long-term heavy-grazing effects on soil and vegetation in the Four Corners region. Southwestern Naturalist 35: 9-14.

Roath, L. R. and Krueger, W. C. 1982. Cattle grazing influence on a mountain riparian zone. Journal of Range Management 35: 100-103. Rocchio, J. 2005. Rocky Mountain subalpine-montane fen ecological system. Ecological Integrity Assessment, Colorado Natural Heritage Program, Colorado State University, Fort Collins, CO.

Rood, S.B., Samuelson, G.M., Weber, J.K., and Wywrot, K.A. 2005. Twentieth-century decline in streamflows from the hydrographic apex of North America. Journal of Hydrology, 306: 215-233.

Rothrock, J. A., Barten P. K., and Ingman, G. L. 1998. Land use and aquatic biointegrity in the Blackfoot River watershed, Montana. Journal of the American Water Resources Association 34 (3): 565-581.

Sada, D. W., Williams, J. E., Silvey, J. C., Ramakka, J., Summers, P., and Lewis, L. 2001. Riparian area management: a guide to managing, restoring, and conserving springs in the Western United States. Technical Reference 1737-17, Bureau of Land Management, Denver, CO. 70 pp. Sada, D. W. and Vinyard, G. L. 2002. Anthropogenic changes in biogeography of Great Basin aquatic biota. Smithsonian Contributions to the Earth Sciences, Volume 33: 277-293.

Schultz, T. T. and Leininger, W. C. 1990. Differences in riparian vegetation structure between grazed areas and enclosures. Journal of Range Management 43: 295-299.

Strand, M., and Merritt, R. W. 1999. Impacts of livestock grazing activities on stream insect communities and the riverine environment. American Entomologist 45: 13–29.Sugden, B. D. and Woods, S. W. 2007. Sediment production from forest roads in western Montana. Journal of the American Water Resources Association 43(1): 193-206.

Teves, N. B. and Stednick, J. D. 2005. Effectiveness of forestry related best management practices in the Trout Creek watershed, Colorado. Colorado Water Resources Research Institute, Completion Report No. 202, 121 pp.

Trombulak, S. C. and Frissell, C. A. 2000. Review of ecological effects of roads on terrestrial and aquatic communities. Conservation Biology 14: 18-30.

USDA Forest Service. 2007a. Region 2 sensitive species evaluation form, Ochrotrichia susanae. Available online.

USDA Forest Service. 2007b. Environmental assessment, North Trout Creek Forest Health and Hazardous Fuel Reduction Project, Salida Ranger District, San Isabel National Forest, Chaffee County, Colorado. Available online.

USDA Forest Service. 2007c. Environmental assessment, rangeland allotment management planning on the Salida-Leadville-South Park planning area. Available online.

Vora, R. S. 1988. Potential soil compaction forty years after logging in northeastern California. Great Basin Naturalist 48: 117-120.

Waters, T.F. 1995. Sediment in streams: sources, biological effects and control. American Fisheries Society Monograph 7. Bethesda, Maryland.

Wiggins, G. B. 1996. Larvae of the North American caddisfly genera (Trichoptera). 2nd edition. University of Toronto Press, Toronto, Canada. 457 pp. Winegar, H. H. 1977. Camp Creek channel fencing—plant, wildlife, soil, and water responses. Rangeman’s Journal 4: 10-12.

Prepared By

Celeste Mazzacano, The Xerces Society for Invertebrate Conservation.