Amino acids are limiting nutrients for growth, development, reproduction and fecundity of most insects. Many insects are adapted to grow and develop on foods that are deficient in essential amino acids or diets with protein and amino acid content far less than the optimal balance. These insects have evolved many solutions to survival on low amino acid diets.
Some insects have symbiotic bacteria in their digestive systems that fix atmospheric nitrogen into amino acids. These symbionts receive a steady supply of energy from excess carbohydrates in the insect diet. The excess carbohydrates are the recipient of the nitrogen in the fixation process that in net convert carbohydrates into amino acids and other nitrogenous chemicals.
Other insects blend nitrogen rich food sources with nitrogen poor foods to create a balanced diet. Mosquito larvae feed on detritus deficient in the nitrogen needed for egg production. The adult females feed on blood which creates stress for the insect during its processing. Herbivorous beetles larvae may balance their amino acid intake by eating pollen, which is high in protein. Caterpillars and aphids are notorious overeaters consuming excess food, excreting excess carbohydrates and efficiently acquiring the nitrogen content.
Understanding how insects meet their needs for amino acids helps us understanding the ecological constraints that regulate insect populations.