Anabolia ozburni Milne, 1935
Basis for Listing
Anabolia ozburni (a northern caddisfly) is known prior to 1965 from the northwestern third of the state. Extensive recent surveys; however, have located it from only single sites in Hubbard and Douglas counties (Chippewa Plains and Hardwood Hills subsections) and a series of adjacent sites in Becker and Mahnomen counties (Pine Moraines & Outwash Plains and Hardwood Hills subsections). All recent collections were of adults in June and July. A total of six specimens have been collected since 1965. Anabolia ozburni was listed as a special concern species in Minnesota in 2013.
Mature larvae of A. ozburni are around 2.5 cm (0.98 in.) in length. They are yellow-brown in color with darker, coalescing spots on their head and thorax. They construct tubular cases of twigs and leaf pieces arranged lengthwise. Adults are 1.4-1.8 cm (0.55-0.71 in.) in length with females larger than males. Both genders are brown in color with darker reticulations on the forewings. Specimens of A. ozburni can be confused with the far more abundant A. bimaculata and A. consocia. Of the three species, A. ozburni is the smallest. 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.
Little is known about the specific habitat requirements of A. ozburni. All recent populations have been found in slow-moving streams, often right at their lentic headwaters. Anabolia species tend to be intolerant of habitat disturbance, especially that of the riparian zone since they depend on terrestrial input for their food source and case-building materials.
Biology / Life History
Little is known about the specific life cycle of A. ozburni. Larvae probably spend a year under the water consuming vascular plant tissue before emerging as winged adults during the summer. All adult specimens in Minnesota were caught during June and July.
Conservation / Management
Limnephilid caddisflies in general have decreased throughout Minnesota since the 1950s primarily due to riparian habitat loss. This decrease has been especially profound in the northwestern portion of the state. The loss of A. ozburni from much of its historical range in northwestern Minnesota is alarming and is probably also due to changes in riparian habitat. Establishing buffer zones between human disturbance and potential A. ozburni habitat is probably the best approach to protecting the species. 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).