D3085: 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 field, we measured alfalfa floral temperatures, humidity of the various colors of alfalfa flowers. Additionally, we conducted 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 found that there was no relation to flower color and flower temperature and humidity in the field. Although, we did find a signifcant difference between floral temperature and humdity with ambient conditions. Through foraging tests we confirmed their preference for purple + blue flowers compared to yellow + green, but found there was no signficant difference on time spent foraging between purple + blue and white flowers. We have yet to understand what is driving the preference for the darker alfalfa flowers. Further studies will explore if other floral traits between the colors such as UV pattern or nectar sugar concentration may be driving this preference.