Abstract:  Protein and carbohydrate are two essential nutrients for insects. Protein is the source of amino acids for insect growth, while carbohydrate is the source of energy for activity. These two nutrients play important roles in insect growth, development and reproduction. In the nature, all insects experience heterogeneous nutritional landscapes, and the contents of proteins and carbohydrates in their food including plants or preys generally vary upon species, tissues or developmental stages. Thus, insects may have some strategies to find the food that contains the proper nutritional composition in their living environment so as to make their growth and development reach the optimal status. Geometric framework model has been demonstrated to be a powerful tool to investigate nutritional physiological regulation mechanisms in insects. This model has been extensively used in how insects coordinate different nutrients in food to achieve the balance of life processes, such as growth, development and reproduction. In herbivores, it is shown that the protein/carbohydrate ratio in food combining with environmental factors can affect the growth and development, as well as the immune response of insects. In predatory and social insects, it is shown that they can strictly regulate the intake of protein and carbohydrate nutrients to meet their needs. In model insects, it is shown that protein/carbohydrate ratio in food may have a balancing effect on lifespan and reproduction in insects. In this review, we introduced the working principle of geometric framework model and systematically summarized its application in insects, aiming to provide new ideas for the study of insect nutrition physiology and ecology.

Key words: Protein, carbohydrate, geometric framework model, nutritional regulation, physiology and ecology