WHEAT-GERM HEMICELLULOSE IS AN ABSOLUTE REQUIREMENT FOR GROWTH AND DEVELOPMENT OF THE SOUTHWESTERN CORN-BORER

The southwestern corn borer, Diatraea grandiosella Dyar, is a major pe st of corn, Zea mays L., in the southern United States. To search for plant allelochemicals, chemically defined insect diets are commonly us ed, but southwestern corn borer larvae did not grow and develop unless a subnutritional amount of wheat germ was incorporated in the amino a cid diet. Fractionation led to identification of hemicellulose as the active component which was then characterized. The hemicellulose permi tted insect growth on a protein-free amino acid diet. Microfloral invo lvement was ruled out because larvae grew and developed free of intest inal microbes. Therefore, this insect has an absolute requirement for hemicellulose that has evidently not been demonstrated with other inve rtebrates or vertebrates. This finding is of general interest because hitherto, the contributions of hemicellulose to nutrition have general ly been considered to be associated chiefly with microfloral conversio n to assimilable carbohydrates. Investigations should be conducted to determine whether hemicelluloses are also important or essential for g rowth of vertebrates including mammals by mechanisms that may not have been considered.