Oxyethira ecornuta Morton, 1893
Basis for Listing
When assigned special concern status in 1996, Oxyethira ecornuta (a purse casemaker caddisfly) was known in Minnesota from only a single specimen collected from Itasca State Park in Hubbard County (Chippewa Plains Subsection). Despite extensive sampling, the species has been found at only two additional sites since then with 14 specimens collected in Becker and Mahnomen counties (Chippewa Plains and Hardwood Hills subsections) in 2000 (Houghton and Holzenthal 2003). It has also recently been collected from two sites in Michigan. These collections represent the only known occurrences of O. ecornuta in the United States. Due to the few documented occurrences of O. ecornuta in Minnesota, it was reclassified as a threatened species in 2013.
Caddisfly species can only be identified by examining their abdominal processes under a microscope. Houghton (2012) has developed an identification manual and key to Minnesota caddisflies. Macroscopically, adults of O. ecornuta are about 3.5 mm (0.14 in.) long with light brown wings. Larvae of the genus Oxyethira are 3-4 mm (0.12-0.16 in.) long, are recognized primarily by their exceptionally long, slender mid- and hind legs, and long antennae; with cases flattened, bottle-shaped, and constructed of silk (Wiggins 1996). Larvae and females of O. ecornuta, specifically, are unknown.
This species has not been positively correlated with its natal microhabitat. Larvae of the genus Oxyethira are found in both lakes and streams (Wiggins 1996). The known Minnesota localities of this species are clean, fast-flowing streams with sand and rocky substrates.
Biology / Life History
All collections of O. ecornuta adults occurred in July. No other specific life history data are known for this species. Larvae of O. ecornuta, specifically, are unknown but likely reach peak maturity in early summer. Oxyethira in general are often found within beds of submerged aquatic plants 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. The wide but extremely limited distribution of this species suggests that it may have very specific habitat requirements. The collection locality of O. ecornuta in Minnesota is mostly within the confines of Itasca State Park and has protection from acute habitat disturbance.
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).