Myrmecophytic A cacia species produce food bodies ( FB s) to nourish ants of the P seudomyrmex ferrugineus group, with which they live in an obligate mutualism. We investigated how the FB s are protected from exploiting nonmutualists. Two‐dimensional gel electrophoresis of the FB proteomes and consecutive protein sequencing indicated the presence of several Kunitz‐type protease inhibitors ( PI s). PI s extracted from A cacia F...