Olfactory information processing in honeybee, Apis mellifera, nestmate recognition

We used nestmate recognition as a model system for testing how animals discriminate complex odour mixtures. Olfactory discrimination is important in social recognition in many animal species, yet the methods used by animals to interpret olfactory social signals are poorly understood. Our first hypothesis was that a guard honeybee would develop a new recognition template (the information used to discriminate nestmates from non-nestmates) when exposed to cue compounds. The data supported the conclusion that guard bees can adopt a new template. Our second hypothesis was that a bee's recognition cues must completely match a colony's template to identify that bee as a colony member. We found that if any one of five compounds in a template applied to a guard bee was absent on another bee, then the guard was unlikely to identify that bee as a colony member. Partial absence of the compound resulted in intermediate or low rates of colony-member identification. We next hypothesized that guard bees assess the ratios of compounds in their template (ratio hypothesis). Alternatively, bees might assess the concentration of each compound independently (concentration hypothesis). Our tests of the ratio and concentration hypotheses suggested that each component of the template is important for discrimination. Whereas the data did not fully support the ratio hypothesis, guard bees assessed the concentrations of an incoming bee's recognition cues and evaluated them, at least partially, in the context of other cues. This information was then used to make discriminations between nestmates and non-nestmates.