Associative olfactory learning of honeybees to differential rewards in multiple contexts--effect of odor component and mixture similarity.

Discrimination among differentially rewarding flowers allows honeybees to maximize their foraging efficiency. We studied how honeybees are able to relate to differential positive rewards when the odor representations are either structurally dissimilar, structurally similar (or form a substrate-product duo in planta), or form a binary mixture sharing a common constituent. Bees were tested both in conditioning of the proboscis-extension response (PER) and in a free-flying context. Our results point to honeybees using olfactory associative learning to differentiate between two positively rewarded odors. In PER, subjects discriminated best between dissimilar odors; they initially generalized between similar odors, but eventually learned to discriminate between them. The discrimination between mixtures sharing a common constituent remained poor. Likewise, the difference in visits to low- and high-rewarding flowers of free-flying bees was greater for dissimilar odors than for binary mixtures sharing a common constituent. Consequences of the operant conditioning nature of the free-flying context are discussed.