Brightly coloured beetles that feed on a wide range of plants possess robust metabolic capabilities, thanks to bacteria residing in specialised organs in their digestive tract. The bacterium Stammera provides essential enzymes enabling Cassidinae beetles to digest plant cell wall components efficiently. Researchers from the Max Planck Institute for Biology in Tübingen discovered the ancient origin of this specialised relationship. They found symbiotic leaf beetles exhibit greater species diversity than their non-symbiotic relatives. These findings, exposing the timing of symbiosis dating back sixty-two million years and its pivotal role in adaptation, are published in Current Biology.