Animal well-being and performance greatly relies on different nutrients. However, nutrient assimilation is firstly influenced by feeding behaviour and then by the digestive system, which is diverse among insects and plays a pivotal role in processing food, digesting macromolecules, and absorbing nutrients for metabolism and growth. Working group 1 will identify: aspects influencing feeding behaviour, digestive physiology, morphology and function, establish parameters for monitoring larval health and development during mass rearing, employ nutritional immunology approaches to modulate systemic immunity through interventions of the diet, leverage genetic and genomic tools to select or produce strains with traits that enhance insect performance on specific substrates, and describe in vitro digestion models capable of predicting outcomes from in vivo feeding experiments. These aspects will be shared with WG1-4 to indicate possible interactions and inform WG5 for the development of materials and methods in insect research. A comparative nutrition workshop translating knowledge from well-studied livestock (e..g poultry, pigs, and aquaculture) and well-studied insect-species, to the focus species within this Action will be organized in the second semester.