Arun’s paper reporting the detailed costs and benefits of evolved immune priming is now published! In an exciting earlier study, we had found that flour beetles exposed to the pathogen Bacillus thuringiensis adapted rapidly via the evolution of either immune priming or pathogen resistance. The new work – led by Arun (now at Edinburgh University) and Imroze Khan (now at Ashoka University) – aimed to test whether these distinct evolved immune responses were costly for a suite of fitness-related traits, and whether these costs could explain how the responses evolved. While we find that immune priming does impose some fitness costs, increased basal resistance appears to be surprisingly cost-free. As a bonus, we found that the enhanced level of immune priming was also transferred across generations. The project involved a ton of painstaking work and careful analysis, and we are all quite proud of the paper. Give it a read!