Hydroptila rono Ross, 1941
Basis for Listing
Despite extensive statewide sampling, Hydroptila rono (a species of purse casemaker 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. The species is typically found in western montane streams but has also been collected from high gradient rivers in Pennsylvania and Québec, Canada. The Minnesota population appears to be isolated from these other populations. Since it was known only from a single location in Minnesota, Hydroptila rono was listed as a threatened species in 2013.
The larva, specifically, of H. rono is unknown. That said, mature larvae of the genus Hydroptila range 3–5 mm (0.12-0.20 in.) in length. They have a thickened abdomen with darker head and thorax. Immature larvae are free-living. Mature larvae build a case composed of two silken valves covered with some small sand or silt particles. Adults of H. rono are light brown in color and around 4 mm (0.16 in.). Macroscopically, they are indistinguishable from the several dozen other species of Hydroptilidae known from the state. Adults 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.
Minneopa Creek is a high gradient stream, fairly atypical of southern Minnesota. Beyond such observations, little is known about the specific habitat needs of H. rono except for the dependence of the larva on single-celled algae as a food source. Minneopa Creek is one of only a few rivers in southern Minnesota with some degree of riparian protection as 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.
Biology / Life History
Little is known about the specific life cycle of H. rono. Larvae probably live for a year under the water feeding on algal cells before emerging as winged adults in early summer. Adults were collected in June.
Conservation / Management
Little is known about the specific conservation needs of H. rono. 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. Further research is necessary to identify any additional populations of the species as well as its specific habitat needs.