Basis for Listing

When assigned special concern status in 1996, Limnephilus rossi (a northern caddisfly) had only been documented in Minnesota by the collection of a single specimen from a creek in Washington County (St. Paul-Baldwin Plains and Moraines).  After recent, extensive sampling throughout the state, this species has been relocated at the Washington County site where it appears to be fairly abundant and discovered, albeit only one specimen, at a site in Cook County (Northern Superior Uplands) (Houghton and Holzenthal 2003).  The Washington County site, unfortunately, is in an area of intense urban development.  Due to documentation at only two locations and the high rate of urban development around the Washington County population, the status of Limnephilus rossi was raised to threatened in 2013.

  Description

Caddisfly species can only be identified by examining their abdominal processes under a microscope. Houghton (2012) has developed an identification manual and key to Minnesota caddisfly species.  Macroscopically, adults of L. rossi are 14-15 mm (0.55-0.60 in.) long with dark brown and pale yellow wings that have the appearance of being covered with minute sand grains (irrorate).  Larvae of Limnephilus range up to 23 mm (0.90 in.) and have tubular cases composed of small rock fragments, though plant material is sometimes incorporated (Wiggins 1996). Larvae of L. rossi are known but have not been formally described (Wiggins 1996).

  Habitat

Limnephilus rossi has not been positively correlated with its natal microhabitat in Minnesota. The two Minnesota streams where adults have been collected are separated by almost 450 km (280 mi) but are both rocky high gradient, second order streams.

  Biology / Life History

Adults of L. rossi have been collected in Minnesota from late August to mid-November. Collection dates correspond to latitude with southern specimens being collected in the fall. The peak of the adult flight period is probably early to mid-September. Larvae of this species have not yet been collected in Minnesota, and it is not clear when mature larvae would be present as many Caddisflies in the Limnephilidae family burrow deep into the substrate to undergo diapause (a period of suspended development) during the summer. No other specific life history data are known for this species; however, larvae likely feed on woody debris and microorganisms (Wiggins 1996).

  Conservation / Management

No specific conservation measures or management strategies can be developed for this species until the larval habitat is confirmed. Larvae of Limnephilus and related genera tend to be intolerant of organic pollution and warming water temperatures. Given their dependence on terrestrial material as a food source (Harris and Lawrence 1978; Hilsenhoff 1987; Wiggins 1996; Barbour et al. 1999), they are also likely impacted by modification of their riparian corridors.

  Conservation Efforts in Minnesota

The Cook County site has good riparian protection from the national monument and tribal lands surrounding it.

  References and Additional Information

Barbour, M. T., J. Gerritsen, B. D. Snyder, and J. B. Stribling. 1999. Rapid bioassessment protocols for use in wadeable streams and rivers: periphyton, benthic macroinvertebrates, and fish, Second edition. EPA 841-B-99-002. United States Environmental Protection Agency, Office of Water, Washington, D.C.

Harris, T. L., and T. M. Lawrence. 1978. Environmental requirements and pollution tolerance of Trichoptera. United States Environmental Protection Agency-600/4-78-063.

Hilsenhoff, W. L. 1987. An improved biotic index of organic stream pollution. Great Lakes Entomologist 20:31-39.

Houghton, David C. 2012. Biological diversity of the Minnesota caddisflies (Insecta, Trichoptera). ZooKeys 189:1-389.

Houghton, D. C., and R. W. Holzenthal. 2003. Updated conservation status of protected Minnesota caddisflies. The Great Lakes Entomologist 36(1-2):35-40.

Houghton, D. C., R. E. Dewalt, A. J. Pytel, C. M. Brandin, S. E. Rogers, D. E. Ruiter, E. Bright, P. L. Hudson, and B. J. Armitage. In press. Updated checklist of the Michigan (USA) caddisflies, with regional and habitat affinities. Zoosymposia.

Houghton, D. C., R. W. Holzenthal, M. P. Monson, and D. B. MacLean. 2001. Updated checklist of the Minnesota caddisflies (Trichoptera) with geographic affinities. Transactions of the American Entomological Society 127(4):495-512.

Leonard, J. W., and F. A. Leonard. 1949. Noteworthy records of caddisflies from Michigan, with descriptions of new species. University of Michigan Museum of Zoology Occasional Papers 520, Ann Arbor.

Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.

Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 394 pp.

Ruiter, D. E. 1995. The adult Limnephilus Leach (Trichoptera: Limnephilidae) of the New World. Ohio Biological Survey Bulletin, New Series, 11: 1-200.

University of Minnesota Department of Entomology Insect Collection. 2009. UMSP Trichoptera: caddisflies. University of Minnesota, St. Paul. <http://www.entomology.umn.edu/museum/databases/>. Accessed 05 August 2009.

Wiggins, G. B. 1996. Larvae of the North American caddisfly genera (Trichoptera), Second edition. University of Toronto Press, Ontario, Canada. 457 pp.