Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Thomas Rinderer


The potential of tropical Africanized honey bees to survive through winter was investigated to predict their possible geographical range and density in the United States. Experiments were conducted in cold rooms, at high elevations in tropical mountains, and during a winter season in Germany. The performance and survival of isolated groups of workers and of intact Africanized colonies were compared with those of European origin, and in some experiments, with those of hybrid crosses. In cold rooms, groups of 40 g of Africanized workers exposed to air currents at 15$\sp\circ$C aggregated in different positions and in tighter conformations than European workers, but these differences were not observed in larger groups (1.0 kg) or in colonies exposed to temperatures between 0 and 20$\sp\circ$C. Rates of sucrose syrup removal from feeders by both the small and large groups of Africanized workers were significantly lower than for European groups of the same biomass. In cold room and field experiments with different treatments of initial worker and brood population, the rate of colony weight loss relative to average population did not consistently differ between Africanized, European, and hybrid colonies. Therefore, overwintering Africanized colonies may not exhaust their honey stores earlier than would European colonies. The clearest difference between Africanized and European field colonies in these studies was the earlier mortality of workers and colonies, despite the presence of honey stores. Africanized colonies did not show evidence of the increased worker longevity found in overwintering European colonies. However, Africanized colonies had a decrease in brood production similar to that found in European colonies. Most Africanized colony deaths resulted from attrition of their worker population. Colony mortality was especially high in Africanized colonies when flight was restricted. The increased length of flightless periods associated with increasing latitude, will decrease the density of Africanized bees. Hybrids between Africanized and European bees had intermediate values for most parameters, suggesting that overwintering factors will favor a highly African region in the south of the United States, a transition zone containing hybrid bees further north, and highly European regions beyond this transition zone.