A study investigates the evolution of beneficial bacteria that live inside and on the surface of farming ants. Attine ants farm fungi, in one of the natural world's best-studied mutualistic symbioses. In the 1990s, the picture of this mutualism was expanded to include another partner: an actinobacteria, Pseudonocardia, which lives on the ants' cuticle—their hard exoskeleton—where its cultures are fed by secretions of subcuticular glands. Pseudonocardia is known to kill the fungal pathogen Escovopsis, which might destroy the ants' mutualistic fungus.