Nutrition concerns the chemicals required by an organism for its growth, tissue maintenance, reproduction and the energy necessary to maintain these functions. Many of these chemicals are ingested with the food, but others are synthesized by the insect itself. In some insects, microorganisms contribute to the insect's nutrient pool.

NUTRITIONAL REQUIREMENTS

Most insects have qualitatively similar nutritional requirements since the basic chemical composition of their tissues and their metabolic processes are generally similar. Most of these requirements are normally met by the diet. Some chemicals can only be obtained in the diet: they are essential (Table 4.1). Others may be synthesized by the insect from dietary components. The dietary requirements of a species may sometimes be obscured due to chemicals having been accumulated and passed on from a previous generation.

Despite the overall similarities, major differences in nutritional requirements do occur. These may be the result of evolutionary changes associated with feeding on substrates with quantitatively, and sometimes qualitatively, different balances of nutrient chemicals.

Reviews: Dadd, 1977, 1985; Reinecke, 1985

Amino acids

Amino acids are required for the production of proteins which are used for structural purposes, as enzymes, for transport and storage, and as receptor molecules. In addition, some amino acids are involved in morphogenesis. Tyrosine is essential for cuticular sclerotization (section 16.5.3) and tryptophan for the synthesis of visual screening pigments (Fig. 25.6). Others, γ-aminobutyric acid and glutamate, are neurotransmitters (section 20.2.3.1), and, in some tissues and some insects, proline is an important energy source.