Density-mediated foraging behavioral responses of Rhyzopertha dominica (Coleoptera: Bostrichidae) and Tribolium castaneum (Coleoptera: Tenebrionidae)

Authors: Ponce Jr, Marco; RANABHAT, SABITA - Kansas State University; BRUCE, ALEXANDER - University Of Tennessee; VAN WINKLE, TAYLOR - City Of Kalamazoo; Campbell, James - Jim; Morrison, William - Rob

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2024
Publication Date: 5/28/2024
Citation: Ponce Jr, M.A., Ranabhat, S., Bruce, A., Van Winkle, T., Campbell, J.F., Morrison III, W.R. 2024. Density-mediated foraging behavioral responses of Rhyzopertha dominica (Coleoptera: Bostrichidae) and Tribolium castaneum (Coleoptera: Tenebrionidae). Scientific Reports. 14:12259. https://doi.org/10.1038/s41598-024-62277-8.
DOI: https://doi.org/10.1038/s41598-024-62277-8

Interpretive Summary: Red flour beetle and lesser grain borer are important and destructive post-harvest insect pests that cause significant economic damage worldwide. Many insects often alter production of pheromones to regulate their population levels. When population levels are low or moderate, insects may release volatiles that attract additional individuals to a food source to increase mating opportunities; however, when populations are high, some insect species release volatiles that act as repellents to reduce competition. Both red flour beetle and lesser grain borer produce attractants and repellents, but few studies have examined how population density impacts attraction to food and pheromones in these species, or whether production of attractants and repellents changes from insect-infested grain under increasing population levels. To address this, we varied population levels (from 10-500 adults per jar) on a fixed amount of food and found reduced attraction to food cues in red flour beetles reared under high population levels but not to pheromones. In contrast, we found that rearing lesser grain borers under high population levels elicited 2-4-fold higher captures in traps with pheromones. The relative composition and abundance of volatiles from food exposed to different numbers of beetles varied significantly and was also species-specific, with the compound 1-tridecene acting as a unique odor produced by red flour beetle colonies. Overall, our results suggest that crowding influences the way that insects respond to food and pheromone volatiles that are commonly used in traps to monitor population levels.

Technical Abstract: Tribolium castaneum and Rhyzopertha dominica are cosmopolitan, destructive postharvest pests. Although research has investigated how high densities of T. castaneum affect attraction to the aggregation pheromone by conspecifics, research into the behavioral response of both species to food cues after high density exposure has been lacking despite its importance to foraging ecology. Our goal was to manipulate and observe the effects of crowding on the behavioral response of both species to common food and pheromonal stimuli to determine how the volatile emission patterns from grain differed under increasing densities. Densities 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, while the headspace emissions were examined through gas chromatography coupled with mass spectrometry. Importantly, at least for T. castaneum, crowded conditions attenuate attraction to food-based stimuli, but not pheromonal stimuli. Crowding seemed to have no effect on R. dominica attraction to food and pheromonal stimuli in the wind tunnel, but exposure to high density cues did elicit 2.1–3.8-fold higher captures in traps. 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 protection of commodities.