Rare Species Guide

  Basis for Listing

Despite an extensive, statewide sampling effort, Ironoquia punctatissima (a species of northern caddisfly) is known in Minnesota from only a handful of sites in the southern portion of the state. A total of fourteen adults were found in September of 1973, 1994, 1999, and 2000. All collecting sites are small (< 1 m² (1.2 sq. yd.)) spring habitats in Lyon, Martin, Watonwan (North-Central Glaciated Plains), and Washington (St. Paul-Baldwin Plains and Moraines) counties. Ironoquia punctatissima is widespread in the eastern U.S. where it is, likewise, restricted to very small springs. Small cold-water spring habitats are scarce in southern Minnesota and are extremely vulnerable to urban and agricultural development. Due to the few documented locations of Ironoquia punctatissima in Minnesota and the rarity and vulnerability of suitable habitats, it was designated an endangered species in 2013.

  Description

Mature larvae of I. punctatissima range 20-22 mm (0.79-0.87 in.) in length. They are dark brown in color with darker spots and blotches on the head and thorax. Larval cases are tubular in shape, curved but not tapered, and composed of bark and leaf pieces. Adults are 18–22 mm (0.71-0.87 in.) in length; males are smaller than females. Both genders have light brown wings with darker blotches. Specimens can be definitively identified only by a close examination of the terminal abdominal segments under a microscope. However, their large size and light brown color makes them fairly distinct in appearance among fall-emergent caddisflies. Other common fall species are smaller, darker, or pale orange instead of light brown.

  Habitat

Ironoquia punctatissima larvae are restricted to small streams throughout its range. They are cold water stenotherms and are dependent on terrestrial input for their case-building material. Thus, they are extremely sensitive to changes in the riparian corridor or forest canopy adjacent to the stream.

  Biology / Life History

Little is known about the specific life cycle of I. punctatissima in Minnesota. Larvae probably spend a year under the water consuming filamentous algae and vascular plant tissue. Adults emerge from the streams in the fall and are active on warm evenings in September.

  Conservation / Management

The most important management consideration for I. punctatissima is the protection of its remaining cold-water spring habitats. Most of these habitats have been badly disturbed in southern Minnesota, and regional extirpations have almost certainly occurred due to this habitat loss. Additional I. punctatissima habitats should be sought out, and known habitats should have their riparian zones protected wherever possible. 

Although the Redwood River population (Lyon County) has riparian protection within Camden 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 I. punctatissima.

  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).