In 1908, Bert Porter reported the presence of 73 species of butterflies in the Decorah, Iowa area. Since then, no systematic surveys of the butterflies in the Decorah area have been completed despite extensive habitat changes and degradation of native prairie and timber that have occurred over the past 90 years. In 1998, an extensive survey of the butterflies of Winneshiek County confirmed the presence of 55 species of butterflies. Our findings generated a checklist of the butterflies currently found in Winneshiek County, and were compared to Porter's original list. Unfortunately, the regal fritillary, Speyeria idalia, and several other butterfly species found in 1908 apparently no longer occur in the Decorah area.
Larsen, Kirk J. and Bovee, Jennifer A.
"Changes in the Butterflies (Lepidoptera) of Winneshiek County, Iowa After 90 Years,"
The Great Lakes Entomologist, vol 34
Available at: https://scholar.valpo.edu/tgle/vol34/iss1/7