This symposium volume gives the state of the art in the research on ant-plant interactions. A lot of new data and insights are presented. A thematic grouping of the chapters divides the book into six parts. The first part deals with antagonistic interactions, i.e., the leaf-cutter ants. It appears that leaf-cutters collect a diversity of material, diluting the effect of toxic allelochemicals. They may collect quite inappropriate material; they have been reported to cut and bring back pieces from plastic labels.