The remarkable diversity of plant-feeding insects could be explained by the dynamics of their plant associations, where host plant shifts and specialization onto a small fraction of available plants may promote diversification. Neotropical Adelpha butterflies contain a large number of species, and previous work indicated the colonization of a novel host plant family (Rubiaceae) fueled its rapid diversification. However, accumulating host records indicate wide taxonomic host breadth at family level and below. Here, we categorize Adelpha diet breadth based on known host plant relationships across the Neotropics and from Costa Rica, Ecuador and Brazil. We also use a diet breadth index that identifies plants used in similar ways by Adelpha, pointing to potential plant traits that could facilitate or prevent plant-insect interactions. We find that diet breadth in Adelpha is not likely to change at different geographic scales, and that regional resource specialization was uncommon. Additionally, the diversification fueled by the switch to Rubiacae, appears to have led to some lowland-clade Adelpha species specializing on a restricted subset of host genera and species within Rubiaceae, as well as in Urticaceae. In contrast, the A. serpa-group shows generalization, with each species tending to feed on its own set of several unrelated plant families. Taken together, these results indicate that Rubiaceae and additional plant families appear as important ecological factors that have promoted adaptations in Adelpha and host plant family-level switches have not always had the same effect on diversification, corroborating the importance of Rubiaceae for this butterfly genus. Further research involving detailed phylogenies is needed to investigate associations between changes in diet breadth and speciation events, and test hypotheses of diet evolution.