The Chemosensory Influence of Some Extracts of Brewers' Yeast and Cereal Products on the Feeding Behavior of the Confused Flour Beetle, Tribolium confusum (Coleoptera: Tenebrionidae)1
Extracts prepared from brewers' yeast, unenriched patent flour, bran, and wheat germ were tested for their ability to elicit aggregation and feeding responses in flour beetles. Also tested were amino acids, sugars, fatty acids, and proteins known to occur in cereals, and some compounds isolated from wheat or wheat products. Yeast contained ethanol-soluble and water-soluble components that induced aggregating and feeding responses. Sugars and amino compounds, or combinations of these, are probably involved. Various solvent extracts of wheat germ were the most active of all the cereal extracts tested. This activity was attributed, in part, to certain fatty acids. In tests with fatty acids known to occur in wheat germ, palmitic acid elicited intense aggregating and feeding responses. Maltose stimulated feeding. None of 5 sugars induced aggregations. The stimulating effect of sucrose and glucose varied between tests. Gluten and gliadin were moderately active. Nineteen amino acids known to occur in flour, and wheat starch, glutathione, flavonoids, and methoxyquinones were chemotactically inert. The feeding behavior of flour beetles was explained in terms of the interrelationships between kineses, sensory adaptation, and thresholds.