Rare Species Guide

  Basis for Listing

Until recently, Hydroptila waskesia (a species of purse casemaker caddisfly) was known in Minnesota from only a single locality in Crow Wing County that was collected in 1964. Then, during an extensive, statewide collecting effort, a single, adult specimen was collected in July of 2000 from Hanson Creek in Roseau County confirming the species’ extant status in the state (Laurentian Mixed Forest Province).  The two collecting sites are separated by around 300 km (185 mi.). Likewise, the known Minnesota populations are over 1000 km (620 mi.) from other known populations in the eastern and southern U.S., suggesting that the Minnesota populations are near the western edge of the species’ range. Hydroptila waskesia was listed as an endangered species in Minnesota in 2013.

  Description

The larva, specifically, of H. waskesia is unknown. That said, mature larvae of the genus Hydroptila range 3–5 mm (0.1-0.2 in.) in length. They have a thickened abdomen with a darker head and thorax. Immature larvae are free-living. Mature larvae build a case composed of two silken valves covered with some small sand or silt particles. Adults of H. waskesia are light brown in color and around 4.0 mm (0.16 in.). Macroscopically, they are indistinguishable from the several dozen other species of Hydroptilidae known from the state. Adults can be definitively identified only by a close examination of the terminal abdominal segments under a microscope. Houghton (2012) has developed an identification manual and key to the caddisflies of Minnesota.

  Habitat

Little is known about the specific habitat needs of this species beyond the dependence of the larva on single-celled algae as a food source. Hanson Creek is a slow-moving, silt-bottomed tributary of the Roseau River. Agricultural disturbance is heavy in the region, and Hanson Creek is one of the few Roseau tributaries with some degree of riparian protection remaining.

  Biology / Life History

Little is known about the specific life cycle of H. waskesia. Larvae probably live for a year under the water feeding on algal cells before emerging as a winged adult in summer. In Minnesota, specimens of H. waskesia have been collected in mid-July and early August.

  Conservation / Management

Little is known about the specific conservation needs of H. waskesia. In general, streams of northwestern Minnesota have been badly degraded by agricultural development, with many regional caddisfly species extirpations. This makes the protection of Hanson Creek, and other fairly undisturbed streams in the region, of paramount importance. Any future development of the riparian corridor of the creek or any changes that would decrease water quality or increase water temperature should be approached cautiously to preserve this isolated population. Further research is necessary to identify any additional populations of the species as well as its specific habitat needs.

  References and Additional Information

Blickle, R. L. 1979. Hydroptilidae (Trichoptera) of America north of Mexico. New Hampshire Agricultural Experiment Station Bulletin 509. University of New Hampshire, Durham. pp. 1-101.

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

Houghton, D. C. 2007. The effects of landscape-level disturbance on the composition of Minnesota caddisfly (Insecta: Trichoptera) trophic functional groups: evidence for ecosystem homogenization. Environmental Monitoring and Assessment 135(1-3):253-264.

Houghton, D. C., and D. W. Holzenthal. 2010. Historical and contemporary biological diversity of Minnesota caddisflies: a case study of landscape-level species loss and trophic composition shift. Journal of the North American Benthological Society 29(2):480-495.

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.

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.