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Response of field populations of Delldroetoll1lS frontalis Zimmermann to their aggregating pheromone was correlated with pheromone content of dissectted hindgut tissues of adult beetles a determined by the gas-liquid chromatography (GLC) technique. Adult beetles in various stages of feeding activity and reproductive states were used for this purpose. Two major components of the aggregating pheromones, frontalin and trans-verbenol, were found in the largest quantities in emergent unfed females. After 48 hours of feeding, frontal in content of the hindguts was 29% and trans-verbeno content was only 5% of that of emergent females. Continuous bioassays of females feeding in host material showed increasing response of field populations to the beetle until 24-48 hours after feeding had begun, then response declined. The fact that pheromone content declined steadily following beetle attack while field response increased was thought to be due to capture of the pheromone in frass particles, thus slowing its rate of release. The decline of pheromone components in hindguts of mated females was not precipitous or abrupt a suggested by behavioral studies on other species of DendroctollllS. Field bioassays confirmed the GLC studies and showed that in both virgin and mated females peak attractiveness occurred 24-48 hours after the tree was attacked the beetles.


Posted with permission of the Entomology Society of America



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