Rare Species Guide

 Oxyethira itascae    Monson and Holzenthal, 1993

A Caddisfly 

MN Status:
special concern
Federal Status:


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Minnesota range map
Map Interpretation
North American range map
Map Interpretation

  Basis for Listing

Oxyethira itascae (a purse casemaker caddisfly) was first described in Minnesota in 1993 based on 98 male specimens collected from Clearwater and Hubbard counties in 1988 and 1989 (Monson and Holzenthal 1993; Monson 1994).  Most specimens were collected in and around Itasca State Park (Northern Minnesota Drift and Lake Plains). Additional O. itascae populations were found in north-central (Northern Minnesota and Ontario Peatlands) and northeastern (Northern Superior Uplands) Minnesota (Lauren 1999 and 2000; Houghton et al. 2001).  Despite these additional collections, further inventory work is still needed to find other populations of this species and delineate its complete range in the state.  Oxyethira itascae was listed as a special concern species in Minnesota in 1996.


Caddisfly species can only be identified by examining their abdominal processes under a microscope. Houghton (2012) has developed an identification manual and key to the caddisflies of Minnesota. Macroscopically, adults are about 2.5 mm (0.1 in.) long and have light brown wings. Larvae of Oxyethira are 3-4 mm (0.12-0.16 in.) long with cases flattened, bottle-shaped, and constructed of silk (Wiggins 1996). Larvae and females, specifically, of O. itascae are unknown.


Oxyethira itascae has not been positively correlated with its natal microhabitat. Larvae of Oxyethira have been found in both lakes and streams (Wiggins 1996). Adults of O. itascae have been collected from a variety of ecosystems but seem to prefer meandering silt-bottomed streams. Minnesota populations have not been found near lakes.

  Biology / Life History

Adults of this species have been collected in Minnesota from late June to the end of August with peak adult flight probably occurring in mid-July. No other specific life history data are known for this species. Larvae are unknown, but they likely mature throughout the summer 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.

  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. 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.

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.

Monson, M. P. 1994. The caddisflies (Insecta: Trichoptera) of the Lake Itasca region, Minnesota, and a preliminary assessment of the conservation status of Minnesota Trichoptera. Thesis, University of Minnesota, Saint Paul, Minnesota. 135 pp.

Monson, M. P., and R. W. Holzenthal. 1993. A new species and new records of Oxyethira (Trichoptera: Hydroptilidae) from Minnesota. Journal of the American Benthological Society 12:438-443.

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

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