How do microclimates of Medicago sativa (alfalfa) influence the foraging preference of Megachile rotundata (alfalfa leafcutting bees)?

Alfalfa leafcutting bees (Megachile rotundata) (ALCB) are important pollinators in North America for their use in pollinating crops such as alfalfa (Medicago sativa). Alfalfa produces various colors of flowers, from light flowers of white and yellow, to darker flowers in blue and purple. ALCB tends to prefer darker flowers of alfalfa, but why they tend to prefer darker flowers to lighter flowers is unknown. We will use laboratory and field experiments to investigate how microclimates of alfalfa flowers differ between these lighter and darker flowers and how that may influence the foraging preference of ALCB. In the lab we will investigate how temperature and nectar concentrations affect ALCB foraging preference. In the field, we will measure alfalfa floral temperatures, humidity, and nectar sugar concentrations of the various colors of alfalfa flowers. Additionally, we will conduct a preference test with flower cuttings and ALCB collected in the field, to learn more about the floral preference between these various flower colors. We expect that ALCB will favor 100% artificial nectar no matter the temperature and that the highest feeding rates will be seen at 35 °C. Additionally, we predict that darker alfalfa flowers will be several degrees warmer and have a higher humidity than lighter flowers. This will lead to higher visitation of ALCB to these darker flowers, in cooler conditions, but in warmer temperatures, ALCB will favor the lighter flowers to aid in thermoregulation. This study may show that flower microclimates of alfalfa can influence the pollination and foraging of ALCB.