Eating leftovers: Understanding Tribolium castaneum interactions with previously-infested flour

Tribolium castaneum, the red flour beetle, is a key pest of cereal grains and products that routinely infests food processing facilities. Such facilities represent dynamic environments comprised of patches of resources that vary with respect to size and quality. To examine the influence of patch size, insect density, and initial lifestage on T. castaneum population dynamics, a 4 x 4 x 2 factorial experiment was conducted. Demographic parameters were compared between 60 g, 120 g, 240 g, and 480 g flour patches initially colonized by 50, 100, 200, or 400 T. castaneum adults or larvae. Following the initial 20-week experiment, wind tunnel assays were employed to assess T. castaneum attraction to previously-infested patches, while patch volatilomes were analyzed via gas chromatography-mass spectrometry. Patch size was observed to significantly influence attraction of T. castaneum to previously-infested patches, with increased attraction to 480 g patches. However, this effect was reduced when initial insect densities were high. This may be mediated by the concentrations of benzoquinones and/or 1-pentadecene in the headspace of previously-infested flour, as these were significantly less abundant in the headspace of 480 g patches. Finally, patterns of adult attraction reflected patterns of adult fecundity, with 2-to-3-fold more adults arising from 480 g patches initially infested with 50 or 100 individuals compared to all other treatments. These data emphasize the high precision of chemical information in mediating T. castaneum foraging decisions.