Our goal was to manipulate and observe the density-mediated effects of crowding on the behavioral response of both species to common food-based and pheromonal stimuli, and how the volatile emission patterns from grain differed under increasing densities. To accomplish this, the density of colonies for both species was altered (10–500 adults) on a fixed quantity of food (10 g of flour or whole wheat), then the behavioral response to common food and pheromonal cues was evaluated in a wind tunnel and release-recapture experiment, and the volatiles from the colonies were examined through gas chromatography coupled with mass spectrometry (GC-MS). Importantly, our results suggest that, at least for T. castaneum, crowded conditions attenuates attraction to food-based stimuli, but not pheromonal stimuli. Crowding seemed to have no effect on R. dominica response to food stimuli at the densities tested. The relative composition and abundance of headspace volatiles emitted varied significantly with different densities of beetles and was also species-specific. Overall, our results have implications for behaviorally-based management tactics that may be able to improve the sustainability of post-harvest agriculture.