Land conversion for agriculture or urban expansion has fragmented the midwestern landscape and isolated native biotas in remnant habitat patches. Identification of priority renmants to be targeted for conservation, however, requires an understanding of the species diversity and distributions in such fragmented landscapes. During a 3-year inventory, we estimated the species richness of Lepidoptera in forests and old fields within an agricultural region of southwest Ohio, Butler County. A combination of casual collecting (butterflies) and a systematic field study (moths) were used to sample lepidopteran species at several sites from 1998-2000. Our inventory added 207 new species to the checklist of the Lepidoptera of Butler County, bringing the total described species richness of the region to 599 species (including Peoria tetradella (Pyralidae), a state record). The species accumulation curve produced from our 1999 moth inventory did not reach saturation, suggesting that additional species remain to be recorded. These results indicate that even highly modified landscapes can support a substantial species diversity of Lepidoptera if there are sufficient areas of native habitat. Since short-term insect inventories tend to be biased toward common, well-known species, rapid diversity assessments may miss important elements of conservation interest. Checklists should remain an important data source for species occurrences and biogeography. Without a well-established knowledge of species geography, critical areas of conservation interest may be overlooked or left unprotected
