Predator-prey interactions can have important consequences for the flow of nutrients through food webs and ecosystems. Given the diversity of predator-prey interactions, it is infeasible to directly measure predator nutrient intake when feeding on each potential prey. Elements are an important measure of nutrient flow through food webs but do not fully account for variation in the quality of nutrients in which they are present. The overall goal of this study was to test if measures of macronutrients, metabolizable protein and lipid, could be used to improve measures of elemental ingestion by predators when feeding on prey. This experiment used two prey that differed widely in exoskeleton content (i.e., larval vs. adult mealworms) because arthropod prey vary widely in this trait and it has the potential to complicate nutritional measurements since it contains nitrogen but is indigestible to most predators. Our results show that the elemental content of whole prey was a poor predictor of elemental consumption by predators. Macronutrient content of whole prey was a strong predictor of macronutrient ingestion by predators, which suggested that it may be a useful measure of predator consumption. Using macronutrient data to create a hybrid element-macronutrient measure of whole prey resulted in better predictions of total elemental ingestion by predators. These results suggest that combining elemental and macronutrient approaches in the study of trophic transfers of nutrients, especially during predator-prey interactions, has the potential to increase our ability to understand and predict the flow of nutrients through food webs and ecosystems.

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Commercialized bumble bees (Bombus) are primary pollinators of several crops within open field and greenhouse settings. However, the common eastern bumble bee (Bombus impatiens Cresson, 1863) is the only species widely available for purchase in North America. As an eastern species, concerns have been expressed over their transportation outside of their native range. Therefore, there is a need to identify regionally appropriate candidates for commercial crop pollination services, especially in the western U.S.A. In this study, we evaluated the commercialization potential of brown-belted bumble bees (Bombus griseocollis De Geer, 1773), a broadly distributed species throughout the U.S.A., by assessing nest initiation and establishment rates of colonies produced from wild-caught gynes, creating a timeline of colony development, and identifying lab-reared workers’ critical thermal maxima (CTMax) and lethal temperature (ecological death). From 2019 to 2021, 70.6% of the wild-caught B. griseocollis gynes produced brood in a laboratory setting. Of these successfully initiated nests, 74.8% successfully established a nest (produced a worker), providing guidance for future rearing efforts. Additionally, lab-reared workers produced from wild-caught B. griseocollis gynes had an average CTMax of 43.5°C and an average lethal temperature of 46.4°C, suggesting B. griseocollis can withstand temperatures well above those commonly found in open field and greenhouse settings. Overall, B. griseocollis should continue to be evaluated for commercial purposes throughout the U.S.A.