Role of ground trash volatiles in the selection of hibernation sites by boll weevils.

Volatiles play a large role in governing the behavior of boll weevils (Anthonomus grandis Boheman). They are attracted to cotton plants, and the female is sexually attracted to the male. The attracting compounds in both instances are terpenoids. Primarily in the fall of the year, boll weevils seek hibernation sites in leaf trash, where they remain until the following spring or summer. In the present study, essential oils were prepared by steam distillation from several leaf samples known to be prevalent at hibernation sites, and the oils were analyzed by GLC-MS. On the basis of the resulting presumptive identifications by comparison with those of standards, a number of mixtures were formulated and were field tested, as were the essential oils. The field tests failed to support unambiguously the premise that boll weevils select hibernation sites on the basis of leaf odor alone. However, in the presence of the sex pheromone, beta-caryophyllene (P > T = 0.08), or a mixture of three sesquiterpene hydrocarbons (P > T = 0.10), or a mixture of alkyl alcohols (P > T = 0.15) increased captures. The response to formulations of the sex pheromone with beta-caryophyllene may be primarily sexual, based on its presence in female boll weevils.

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 pest of corn, Zea mays L., in the southern United States. To search for plant allelochemicals, chemically defined insect diets are commonly used, but southwestern corn borer larvae did not grow and develop unless a subnutritional amount of wheat germ was incorporated in the amino acid diet. Fractionation led to identification of hemicellulose as the active component which was then characterized. The hemicellulose permitted insect growth on a protein-free amino acid diet. Microfloral involvement was ruled out because larvae grew and developed free of intestinal microbes. Therefore, this insect has an absolute requirement for hemicellulose that has evidently not been demonstrated with other invertebrates or vertebrates. This finding is of general interest because hitherto, the contributions of hemicellulose to nutrition have generally been considered to be associated chiefly with microfloral conversion to assimilable carbohydrates. Investigations should be conducted to determine whether hemicelluloses are also important or essential for growth of vertebrates including mammals by mechanisms that may not have been considered.