Digestibility and nutrient composition of foodstuffs, be they plant or not, and the nutritional requirements of insects vary. The qualitative nutritional requirements among insects are quite similar. Therefore, qualities of foodstuff as measured by its ability to promote or support growth, etc. depend on how well the nutrient composition of foodstuff made available by digestion fits the nutritional requirements of the insect. This is better seen using synthetic diets rather than plants. From such investigations it is found that, provided all essential nutrients are present, the proportions of essential nutrients in a foodstuff contribute more to nutritional quality than do the absolute amounts of nutrients. Thus, nutrient balance per se can affect: rate of food consumption and efficient utilization; parasites with respect to host food; rate of growth and development as such, and with respect to temperature; and food selection in an insect.The purpose of this paper is to draw attention to quantitative factors of nutritional importance, especially the proportions of nutrients in foodstuff. These factors are concerned with the nutritional qualities of insect foodstuff, be it plant or any stuff used as food, and their effects are measured by the ability of the foodstuff to promote or support growth, development, survival and reproduction of an insect. For insects have to obtain specific essential food substances, or nutrients, which are needed as nutritional requirements for body material and energy to do all the things attributed to life. But though food abundance is generally recognized as one of the major biotic factors regulating the numbers and population fluctuations of insect species, the nutritional qualifies of the foodstuff are not given due consideration in these matters. This paper will concern plants, for nutritionally important substances are basic to insect/food-plant relationships, and is important because about half of the known species of insects feed on plants.However, the usefulness of plants to show such nutritional matters is severely limited for various reasons (Beck, 1956; Friend, 1958;Auclair, 1958; House, 1961). And in no case have the,, nutritional requirements of a phytophagous insect together with the digestibility and nutritive composition of its food plant been determined completely enough for the purpose at hand. But synthetic, or chemically defined, diets have been used that permitted the physical and chemical properties of the foodstuff, including its digestibility, to be kept uniform and the nutrient