Cuthrell, D.L. 1991. The butterflies of Kittson and Roseau counties, MN, with special emphasis on the dakota skipper (Hesperia dacotae) [Skinner]. Final report submitted to Nongame Wildlife Program, Minnesota Department of Natural Resources. 48+ pp.
The survey of Kittson and Roseau counties for rare butterflies was conducted from May - August 1991, during various butterfly flight periods. In addition to the Dakota Skipper, a total of 13 butterflies were chosen as survey species because of their current state status or because an assessment of their habitat requirements and distribution within Minnesota was desired. Many of the species are confined to narrowly defined plant community types so sites were selected in such a way as to match specific habitats with associated butterfly species. Survey sites were selected by using several different sources of information including: aerial photo interpretation, soil surveys, historic butterfly records, discussions with MN DNR staff, area wildlife managers, and state park naturalists. In addition, roadside reconnaissance was used to evaluate sites selected by the above methods and to identify new sites.
Dakota Skipper populations were located at only three of the 37 sites surveyed between June 18 and July 15, 1991. The skipper was not seen at the historic site during 1991 despite five visits to the area. It must be noted, however, that the weather at the suspected peak of adult activity was extremely cloudy and wet, with July 1991 being one of the wettest July's on record for Kittson County. The largest population of the skipper was found within Lake Bronson State Park. On June 18, 8 male and 4 female skippers were seen here. On June 22, 4 females and 11 males were seen in the same area. Two new sites for the state endangered Assiniboia skipper, Hesperia comma assiniboia, were recorded during the 1991 survey. A large breeding population was found at Norway Dunes, a Nature Conservancy preserve in Kittson County. The Poweshiek skipperling, Oarisma poweshiek, another prairie restricted skipper, was recorded from Roseau County for the first time at two sites. In addition, this state listed special concern butterfly was found at nine new Kittson County sites. The tiny Bog copper, Epidemia epixanthe michiganensis, was recorded in Roseau County for the first time, at four different locations. This butterfly was observed in 1991 for only seven days. Five new Roseau County sites were recorded for the bog restricted Frigga fritillary, Clossiana frigga saga. The range of the Bog fritillary, Clossiana eunomia dawsoni, in MN was extended westerly as it was recorded at seven Roseau County sites in just six short days. The Jutta artic, Oeneis jutta ascerta, another bog associated butterfly was found at four Roseau County sites. This also extended the western range in MN for this species. The secretive, early-season-flying Red-disked alpine, Erebia discoidalis, was discovered at six new sites in Roseau County. The Dorcas copper, Epidemia dorcas, was recorded at 20 new sites throughout the survey counties from July 9 to August 4, 1991. Three other target species were not found including Freija fritillary, Clossiana freija, the Disa alpine, Erebia disa mancinus, and the Uhler's arctic, Oeneis uhleri.
Re-survey is needed at some sites which were insufficiently covered due to both weather and time constraints. Re-survey along with population monitoring is also recommended within Lake Bronson State Park and at the other two newly discovered sites.