By using harmonic radar, we report the complete flight paths of displaced bees. Test bees forage at a feeder or are recruited by a waggle dance indicating the feeder. The flights are recorded after the bees are captured when leaving the hive or the feeder and are released at an unexpected release site. A sequence of behavioral routines become apparent: (i ) initial straight flights in which they fly the course that they were on when captured (foraging bees) or that they learned during dance communication (recruited bees); (ii ) slow search flights with frequent changes of direction in which they attempt to ''get their bearings''; and (iii ) straight and rapid flights directed either to the hive or first to the feeding station and then to the hive. These straight homing flights start at locations all around the hive and at distances far out of the visual catchment area around the hive or the feeding station. Two essential criteria of a map-like spatial memory are met by these results: bees can set course at any arbitrary location in their familiar area, and they can choose between at least two goals. This finding suggests a rich, map-like organization of spatial memory in navigating honey bees.dance ͉ communication ͉ localization in navigation ͉ vector orientation ͉ vector map

Memory retrieval initiates two consolidation processes: consolidation of an extinction memory and reconsolidation of the acquisition memory. The strength of the consolidation processes depends on both the strength of the acquisition memory and the strength of retrieval trials and is correlated with its sensitivity to inhibition. We demonstrate that in the honeybee (Apis mellifera), memory retrieval of a consolidated appetitive olfactory memory leads to both consolidation processes, depending on the number of retrieval trials. Spontaneous recovery from extinction is induced by many (five), but not by few (one and two), retrieval trials. Spontaneous recovery is blocked by emetine, an inhibitor of protein synthesis. We conclude that reconsolidation of the acquisition memory underlies spontaneous recovery.

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Conditioned behavior as observed during classical conditioning in a group of identically treated animals provides insights into the physiological process of learning and memory formation. However, several studies in vertebrates found a remarkable difference between the group-average behavioral performance and the behavioral characteristics of individual animals. Here, we analyzed a large number of data (1640 animals) on olfactory conditioning in the honeybee (Apis mellifera). The data acquired during absolute and differential classical conditioning differed with respect to the number of conditioning trials, the conditioned odors, the intertrial intervals, and the time of retention tests. We further investigated data in which animals were tested for spontaneous recovery from extinction. In all data sets we found that the gradually increasing group-average learning curve did not adequately represent the behavior of individual animals. Individual behavior was characterized by a rapid and stable acquisition of the conditioned response (CR), as well as by a rapid and stable cessation of the CR following unrewarded stimuli. In addition, we present and evaluate different model hypotheses on how honeybees form associations during classical conditioning by implementing a gradual learning process on the one hand and an all-or-none learning process on the other hand. In summary, our findings advise that individual behavior should be recognized as a meaningful predictor for the internal state of a honeybee-irrespective of the group-average behavioral performance.Learning and memory formation in vertebrates and invertebrates have been studied on the basis of a large range of classical and operant conditioning paradigms. Typically, the interpretation of experimental results relies on performance measures that were derived by averaging over behavioral observations from identically treated animals. However, several studies have recognized the inadequacy of group-average measures to capture the characteristics of individual behavior and, consequently, the learninginduced changes in individual brains (Krechevsky 1932;Restle 1965;Hanson and Killeen 1981;Estes 2002;Brown and Heathcote 2003;Cousineau et al. 2003). Most notably, Gallistel et al. (2004) found that the gradually increasing learning curve observed in many vertebrate learning paradigms reflected an artifact of group averaging. The behavioral performance of individuals appeared to be characterized by an abrupt and often step-like increase in the level of response.To our knowledge and in contrast to the vertebrate literature (see Gallistel et al. 2004), surprisingly little is known of a possibly heterogeneous expression of behavior for the most frequently applied invertebrate conditioning paradigms. For the fruit fly (Drosophila melanogaster) it appears to be common sense that the group-average behavioral measures adequately represent the probabilistic expression of behavior in individuals-a notion that goes back to an early study by Quinn et al. (1974).In the following,...