Honeybee guards do not use food-derived odors to recognize non-nest mates: a test of the Odor Convergence hypothesis

Honeybee (Apis mellifera) colonies rob honey from each other during periods of nectar shortage. Persistent robbing can kill weak colonies. Primarily responsible for preventing robbing are guard bees. Previous research has shown that the probability of both nest mate and non-nest mate workers being accepted by guards at the nest entrance increases as nectar availability increases. The mechanism responsible for this change in guard acceptance can be explained by two competing hypotheses: Odor Convergence and Adaptive Threshold Shift. In this study we tested the Odor Convergence hypothesis. The acceptance by guards at the nest entrance of workers transferred between four colonies that had been fed either odorless sucrose syrup (two colonies) or diluted heather honey (Calluna vulgaris) (two colonies) was measured for 3 days before feeding and during 2 weeks of feeding. Despite the large sample sizes, the probability of guards accepting non-nest mates was not affected by the similarities or dissimilarities in food odor between guards' and non-nest mates' colonies. This finding contrasts with the accepted wisdom that food odors are important in nest mate recognition in honeybees and the data, therefore, strongly reject the Odor Convergence hypothesis.