Recognition of complex odors by restrained and free-flying honeybees, Apis mellifera

Complex odor recognition in the honeybee was investigated using two behavioral assays: (1) the conditioning of the proboscis extension (CPE) with restrained individuals, and (2) the observation of foragers visiting an artificial feeder in a flight room. Nine compounds, previously identified as oilseed rape flower volatiles, were tested either individually or in mixtures. Different sets of experiments were done to determine: (1) the acquisition rate of the nine compounds in the CPE assay, and (2) the discrimination of the individual compounds after conditioning to a mixture, using the CPE assay and free-flying foragers. After conditioning to a complex mixture, honeybees established a hierarchy among the components, with some of them accounting for a major part of the behavioral activity of the mixture. Both behavioral assays led to the same classification of compounds, indicating good agreement between discriminating abilities of restrained individuals and of a population of foragers. The key compounds for recognition of these mixtures were those that were well learned when presented individually. However, the recognition of some compounds was affected by the other components of the mixture, with the activity of some compounds being either enhanced or reduced.