Rubber plantation has become the most dominant human-modified landscape in continental Southeast Asia. Despite many studies documenting ecological impacts of rubber plantations, little attention has been paid to arboreal ant fauna which represent major biomass in tropical rainforests. We used canopy bait trapping to capture ants from individual trees of rubber plantations and natural rainforests in monsoonal Xishuangbanna, southwest China. The survey was repeated in dry and wet seasons to investigate seasonal variation. Not surprisingly, abundance and species richness of arboreal ants were higher in rainforests than rubber plantations in both wet and dry seasons, reflecting habitat complexity of the rainforest canopies. Assemblage composition of arboreal ants was seasonally variable in the rainforests, whereas such seasonal variation was not observed in the rubber plantations. We hypothesized that rainforests present highly heterogeneous microhabitats with climate refugia where colonies of some ant species can persist over dry and cold winters. In contrast, such refugia may be absent in the rubber plantation where only ant species that are ‘robust’ against climatic variability can survive (hence no seasonal changes). Our study suggests that habitat homogenization not only causes reduction in diversity but diminishes seasonal dynamics of arboreal ant fauna as well.