Lepidostoma libum Ross, 1941
Basis for Listing
Despite extensive, statewide sampling, Lepidostoma libum (a species of caddisfly) is known in Minnesota from only two adult specimens collected from Minneopa Creek in Minneopa State Park (Minnesota River Prairie Subsection) in June of 2000. Minneopa Creek is one of only a few rivers in southern Minnesota with some degree of riparian protection where it flows through the state park. Elsewhere however, Minneopa Creek has been, like most rivers of the area, badly degraded by agriculture and urban development. Due to its documentation in only one stream, its sensitivity to habitat disturbance, and the high degree of habitat degradation in southern Minnesota, Lepidostoma libum was designated threatened in 2013.
Mature larvae of L. libum are around 13 mm (0.51 in.) in length. They are dark brown in color with small light spots on the head and thorax. Larval cases are tubular, distinctly four-sided, and constructed of quadrate bark or leaf pieces. Adults are light brown in color and 8-10 mm (0.31-0.39 in.) in length; males are smaller than females.
The specific habitat needs for L. libum in Minnesota are unknown. In general, Lepidostoma species are found in depositional areas of streams with high levels of riparian canopy cover. In other states, L. libum is found in small spring habitats with dense canopy cover. It is stenothermic and is also highly sensitive to changes in riparian habitat as it is dependent on terrestrial input for its food source and case-building materials.
Biology / Life History
Little is known about the specific life cycle of L. libum in Minnesota. Larvae probably spend a year under the water consuming detritus and other organic matter before emerging as a winged adult in early summer. The two adult specimens from Minnesota were caught in June.
Conservation / Management
The majority of aquatic habitats in southern Minnesota have been degraded through agricultural and urban development, with many regional extirpations as the result. Although Minneopa Creek has riparian protection within Minneopa State Park, it is under continual threat from agriculture and development outside the park. 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 of L. libum. Further research is necessary to identify any additional populations of the species as well as its specific habitat needs.
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. 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. 2005. Field guide to the native plant communities of Minnesota: the prairie parkland and tallgrass aspen parklands provinces. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 362 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.
Weaver, J. S. 1988. A synopsis of the North American Lepidostomatidae (Trichoptera). Contributions of the American Entomological Institute 24(2):1-141.
Wiggins, G. B. 1996. Larvae of the North American caddisfly genera (Trichoptera), Second edition. University of Toronto Press, Ontario, Canada. 457 pp.