Self-selection of an optimum diet from a mixture of wheat fractions by the larvae of Tribolium confusum

Tribolium confusum was reared from the beginning of the first instar to the pupa on wheat bran, endosperm or germ or on a 1 : 1 : 1 mixture of these three fractions. The food intake of the larvae reared on the mixture included more or less similar proportions of the three wheat fractions, averaging 1·5 per cent bran, 17·1 per cent endosperm and 81·4 per cent germ. Past work on the nutrition of stored-product insects has involved the assumption that the insects cannot feed selectively from a finely powdered diet. Our findings show that this assumption may not be warranted. The mixed diet supported growth better than any one of the pure fractions or any wheat diet previously tested by us. It was superior to germ, the best of the pure fractions, because it was more digestible and because the digested portion was more efficiently utilized for growth. Endosperm, the poorest diet of the fractions, was highly digestible but was not efficiently utilized. Bran, better than endosperm but inferior to germ, was relatively indigestible although the digested portion was efficiently utilized. Germ was both digestible and efficiently utilized.