1. Central and Southeast Asia currently faces rapid loss and degradation of tropical and subtropical forests with potentially severe effects on its biodiversity.2. We analysed population characteristics and dispersal of the butterfly Byasa impediens in eleven patches of a fragmented subtropical forest in Western China.3. In an area covering 30 km 2 , we found an unexpected high dispersal capacity of more than 5 km, and estimated a mean dispersal distance of 1 km according to the negative exponential function. However, the inverse power function gave a better fit and predicted a reasonably large fraction of long-distance displacements: 4% of all movements were estimated to exceed 5 km.4. In spite of the high level of fragmentation and small sizes of some patches, we did not observe extinction or (re)colonisation events. Matching dispersal ability with the spatial grain of the resource patches in the landscape is seen as a major cause. In addition, persistence, emigration and immigration of individuals were exclusively affected by the amount of larval host plants, nectar plants and forest cover.5. Our study indicates the importance of long-distance dispersal and shows that species with large dispersal abilities and a somewhat broader dietary niche, such as B. impediens, can sustain in fragmented areas if patch quality is sufficient.6. We suggest that conservation action may not only focus on particularly endangered species but also on relatively common, but often endemic, insect species. This is of particular concern given the global dominance of insects and their importance for ecosystem services, especially in an area of constantly increasing demands of agricultural products.