Cooperation shapes social interactions, influencing individual success and driving the evolution of complex biological systems like multicellular organisms and insect societies. Evolutionary theory explains how cooperation emerges among kin and non-kin when fitness benefits outweigh personal costs. The key challenge is no longer why cooperation evolves, but how—what conditions favor it, and how diverse are its phenotypes? Current studies focus on a few model organisms, mainly birds, fish, and microbes, many of which are unsuitable for high-replication lab studies. Additionally, manipulating costs and benefits is difficult, limiting experimental tests of when cooperation persists, collapses, or shifts under ecological and social changes like disease pressure or group relatedness.This project will establish Tribolium beetles and their pathogens as a novel model for studying cooperation, allowing precise control over relatedness and costs via infection risk. Infectious disease is a powerful but overlooked tool for cost manipulation, as infection severity and transmission mode (airborne vs. foodborne) can be adjusted, with the latter being less harmful. Using infections, behavioral tracking, kin discrimination, and fitness assays, this project will investigate how individuals adjust cooperation under varying costs. Fitness effects will be assessed through mathematical modelling, providing a long-term perspective on evolutionary stability of found behaviours. Environmental factors also shape cooperation, yet little is known about Tribolium habitat interactions. This project will be the first to examine their tunnel-digging behavior and spatial organization, providing ecological context to cooperation. By integrating disease ecology, chemical ecology, and kin selection theory, this interdisciplinary approach will offer novel insights into cooperation and disease defense in animal groups.