Butterfly assemblages were investigated using route census surveys, at Flowertown in Sanda from April to October, 1994. In order to evaluate the naturalness of vegetation through the species composition of butterflies, we proposed a butterfly index, which indicated the degree of naturalness of the habitat. The values of species diversity, averages of the butterfly index, and values calculated by the Bray-Curtis ordination method were calculated for eight vegetational conditions ; outside fragmented forest ; inside fragmented forest ; outside grassland ; inside grassland ; park ; detached house ; multiple dwelling house ; bare area. The results showed that the species diversity and butterfly index were highest in fragmented forests, and were lowest in the bare area. Ecological distribution of butterflies was classified into four types ; forest-type ; grassland-type ; park-type ; others. Many butterflies belonged to the forest-type classification, since there were many plant communities in the fragmented forests, such as Rhododendro macrosepali-Pinetum densiflorae, Quercetum variavili-serratae, Alnus japonica-Ligustrum obtusifolium Comm. Apanantho-Celtidetum japonicae, Querces acutissima Comm. etc. It seemes that fragmented forests are a very important habitat for butterflies, in spite of the small size of such forests. Butterfly assemblages at Flowertown were compared with other localities, including Mino Park, Hattori-ryokuchi Park, Osaka Castle Park, etc. Mino Park, Mt. Nijosan and Mt. Sanageyama were estimated to be at the secondary vegetational stage, while Osaka Castle Park, Nagai Park and Daisen Park were estimated to be at the urban stage. Although Flowertown was at the secondary vegetational stage in terms of butterfly fauna, it was at the residential-urban stage in terms of butterfly assemblages.