Limnephilus secludens Banks, 1914
Basis for Listing
Limnephilus secludens (a species of northern caddisfly) was the single most widespread caddisfly in northwestern Minnesota prior to 1950. It was also collected sporadically from the southern and northern portions of the state. More recently, despite extensive sampling for caddisflies throughout the state, only a single specimen of L. secludens has been found. This adult specimen was discovered in September of 1999 in a small (<0.5m (<1.6 ft.) wide) unnamed stream near Watkins Lake in Martin County (Prairie Parklands Province). Small undisturbed stream habitats are now extremely rare in the northwestern and southern regions of Minnesota due to agricultural and urban development, and the precipitous decline in L. secludens within Minnesota is almost certainly a direct result of this habitat loss. Limnephilus secludens was listed as an endangered species in Minnesota in 2013.
The larva, specifically, of L. secludens is unknown. Mature larvae of the genus Limnephilus range 20-30 mm (0.79-1.2 in.) in length, and they are variable in coloration. Larval cases can be composed of wood pieces, pebbles, or leaves. Adults of L. secludens are 18-20 mm (0.71-0.79 in.) in length; females are larger than males. Both genders are light brown in color without patterning on the wings. They are very difficult to distinguish from the 18 other Limnephilus species known from Minnesota. Specimens 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.
Although the specific habitat requirements of L. secludens have not been established, species of Limnephilus are very sensitive to changes in the riparian corridor since they depend on terrestrial input for their food and case-building material. Historical records of L. secludens are from streams of varying size.
Biology / Life History
Little is known about the specific life cycle of L. secludens. Larvae probably spend a year under the water consuming woody debris or plant tissue. In Minnesota, most adult specimens have been caught in June and July.
Conservation / Management
Given the precipitous decline of this species within the last few decades and the loss of small undisturbed streams in the northwestern and southern portions of the state over the same time period, identifying and protecting remaining L. secludens habitats is of primary importance. Any future development of the riparian corridor of such habitats or any changes that would decrease water quality or increase water temperature should be approached cautiously to preserve isolated populations of L. secludens. At the very least, establishing riparian buffer zones between human disturbance and L. secludens habitat would likely benefit the species.
References and Additional Information
Flint, O. S. 1960. Taxonomy and biology of some Nearctic limnephilid larvae (Trichoptera), with special reference to species in eastern United States. Dissertation. Cornell University, Ithaca, New York.
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.
Ruiter, D. E. 1995. The adult Limnephilus Leach (Trichoptera: Limnephilidae) of the New World. Ohio Biological Survey Bulletin, New Series, 11: 1-200.
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.