The honeybee, Apis mellifera, is an invaluable partner in agriculture around the world, both for its production of honey and, more importantly, for its role in pollination. Honeybees are largely unexplored at the molecular level, despite a long and distinguished career as a model organism for understanding social behavior. Like other eusocial insects, honeybees can be divided into several castes: the queen (fertile female), workers (sterile females) and drones (males). Each caste has different energy and metabolic requirements and each differs in its susceptibility to pathogens, many of which have evolved to take advantage of the close social network inside a colony. Hemolymph, arthropods' equivalent to blood, distributes nutrients throughout the bee and the immune components contained within it form one of the primary lines of defense against invading microorganisms. In this study we have applied qualitative and quantitative proteomics to gain a better understanding of honeybee hemoly