Rare Species Guide

  Basis for Listing

When assigned special concern status in 1996, Oxyethira ecornuta (a purse casemaker caddisfly) was known in Minnesota from only a single specimen collected from Itasca State Park in Hubbard County (Chippewa Plains Subsection).  Despite extensive sampling, the species has been found at only two additional sites since then with 14 specimens collected in Becker and Mahnomen counties (Chippewa Plains and Hardwood Hills subsections) in 2000 (Houghton and Holzenthal 2003).  It has also recently been collected from two sites in Michigan. These collections represent the only known occurrences of O. ecornuta in the United States. Due to the few documented occurrences of O. ecornuta in Minnesota, it was reclassified as a threatened species 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 caddisflies. Macroscopically, adults of O. ecornuta are about 3.5 mm (0.14 in.) long with light brown wings. Larvae of the genus Oxyethira are 3-4 mm (0.12-0.16 in.) long, are recognized primarily by their exceptionally long, slender mid- and hind legs, and long antennae; with cases flattened, bottle-shaped, and constructed of silk (Wiggins 1996). Larvae and females of O. ecornuta, specifically, are unknown.

  Habitat

This species has not been positively correlated with its natal microhabitat. Larvae of the genus Oxyethira are found in both lakes and streams (Wiggins 1996). The known Minnesota localities of this species are clean, fast-flowing streams with sand and rocky substrates.

  Biology / Life History

All collections of O. ecornuta adults occurred in July. No other specific life history data are known for this species. Larvae of O. ecornuta, specifically, are unknown but likely reach peak maturity in early summer.  Oxyethira in general are often found within beds of submerged aquatic plants and feed by piercing the cells of filamentous algae and consuming the contents (Wiggins 1996).

  Conservation / Management

No specific conservation measures or management strategies can be developed for this species until the larval habitat is confirmed. Few data are available on general Oxyethira tolerance to anthropogenic disturbances. The wide but extremely limited distribution of this species suggests that it may have very specific habitat requirements. The collection locality of O. ecornuta in Minnesota is mostly within the confines of Itasca State Park and has protection from acute habitat disturbance.

  Conservation Efforts in Minnesota

Field surveys in conjunction with a University of Minnesota study on the Caddisflies of Minnesota (Houghton et al. 2001) have been conducted to search for additional populations of this species, and an identification manual and key to Minnesota caddisflies has been developed (Houghton 2012).

  References and Additional Information

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

Houghton, D. C. 2002. Biodiversity of Minnesota caddisflies (Insecta: Trichoptera). PhD Thesis, University of Minnesota, Minneapolis, Minnesota. 194 pp.

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.

Kelly, Robert W. 1985. Revision of the Micro-caddisfly genus Oxyethira (Trichoptera: Hydroptilidae). Part II: Subgenus Oxyethira. Transactions of the American Entomological Society 111(2):223-253.

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.

Monson, M. P. 1997. The caddisflies of the Lake Itasca region, Minnesota (Insecta: Trichoptera). Pages 309-321 in R. W. Holzenthal and O. S. Flint, Jr., editors. Proceedings of the 8th International Symposium on Trichoptera, 9-15 July 1995, Minneapolis and Lake Itasca, Minnesota. Ohio Biological Survey, Columbus, Ohio.

Morton, K. J. 1893. Notes on Hydroptilidae belonging to the European fauna, with descriptions of new species. The Transactions of the Royal Entomological Society of London 41:75-82.

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.