Factors impacting overwintering success of honey bees, Apis mellifera

Populations of honey bees experience dramatic losses over the winter, with beekeepers in the US losing an average of 30% of their colonies in surveys conducted from 2006 to 2011. Honey bees overwinter in a thermoregulating cluster, and overwintering honey bee workers are in a distinct physiological state compared to summer bees, including altered hormone levels, reduced metabolism, high nutrient stores, and dramatically increased lifespan. Previous studies have suggested that levels of Varroa mites and viruses are strongly correlated with colony losses, but the effects of these factors on overwintering bees at the molecular and physiological level have not been well studied.  Here, we examine the impact of genetic stock (Northern vs Southern reared) on the physiology, parasite and pathogen load, and survival of overwintering honey bees, and characterize the interactions between these factors. This study will not only shed light on the mechanisms regulating overwintering and underlying overwintering success in honey bees, but will also produce valuable information that can be used to develop better management practices for the beekeepers.