The small size of insects, correlated with high food-consumption, growth, and metabolic rates, makes possible their high efficiency of food-utilization, short life cycles, high biotic potential, and rapid genetic adaptation and speciation. Most of the qualitative nutritional requirements are known for many insect species; many essential nutrients are provided by microbial symbiotes. Recent studies in quantitative nutrition make possible more detailed analysis of the utilization of food, of the kinetics of growth and metabolism in intact animals, and of the controlling mechanisms in the animal-food interaction.