Protein and lipid regulation and its effect on honey bee physiology and behavior

Honey bees are arguably the most beneficial insect to modern agriculture, providing pollination services to major agricultural crops and flowering plants. While proper colony nutrition is pivotal for honey bee health, we still lack critical information about honey bee nutritional requirements, particularly with respect to the macronutrients present in pollen. The goal of this study was to identify the patterns of macronutrient consumption that drive honey bee pollen foraging within a nutritional geometric framework. We did so by exploring whether and how honey bees regulate their protein and lipid intake through a combination of laboratory and field choice and no-choice experiments using artificial diets and natural pollen with a similar protein-to-lipid (P:L) ratio, but different levels of fatty acids. In the laboratory experiments, bees consumed the most diet when given a diet with a P:L ratio of 1.5P:1L and regulated their consumption for lipids to a similar ratio when given a pair of nutritionally complementary suboptimal diets. Nurse bees that consumed the 1.5P:1L diet also had significantly larger hypopharyngeal glands compared to bees in all other treatment groups. When given pollen with a similar P:L ratio, but different total fatty acid content and distribution, honey bee foragers significantly preferred to collect Brassica pollen, which has 3x more total fatty acids and has a higher linolenic to linoleic ratio. Our results demonstrated that honey bees regulate their lipid intake, established a P:L ratio for honey bee diets, and highlighted the importance of nutritionally relevant fatty acids in forager decision making.