Rare Species Guide

  Basis for Listing

Hydroptila tortosa (a purse casemaker caddisfly) is known in Minnesota from one specimen collected from Lake County in 1938 (Northern Superior Uplands Section). This species has not been relocated despite searches at a variety of localities near this site (Ludeman 1991; Houghton et al. 2001). Further inventory work is needed to find other populations of this species and delineate its range in the state.  Hydroptila tortosa was listed as a special concern species in Minnesota in 1996.

  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 the  caddisflies of Minnesota. Macroscopically, adults of H. tortosa are about are about 3.0 mm (0.12 in.) long with light brown wings. Larvae of Hydroptila are 3.0-5.0 mm (0.12-0.20 in.) long with cases compressed and composed of two silken valves covered with a layer of sand grains (Wiggins 1996). Larvae and females, specifically, of H. tortosa are  unknown.

  Habitat

Hydroptila tortosa has not been positively correlated with its natal habitat. Larvae of Hydroptila are found in both lakes and streams (Wiggins 1996). The collection site in Minnesota is located near several small streams as well as the Baptism River.

  Biology / Life History

The only known Minnesota collection of H. tortosa adults occurred in July. No further specific life history data are known for this species. Larvae are unknown but likely reach peak maturity in early summer and likely 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 Hydroptila 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., 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.

Ludeman, J. 1991. A preliminary survey for endemic species, and restricted or disjunct populations of caddisflies in Minnesota. Report submitted to the Minnesota Department of Natural Resources. 7 pp.

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.

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