The significance of landmarks for path integration in homing honeybee foragers

During their complex foraging trails, central place foragers often integrate distances traveled and angles turned to update continuously their estimation of home direction. This system, called path integration, allows them to head directly home even from an unfamiliar site [i]. Path integration has been particularly well studied in ants [21. Honeybees, Api s mellifera L., forced to deviate from straight lines between hive and a feeder by means of obstacles, indicate the actual compass direction of the target in their dances [3]. Thus, honeybees convey the results of path integration in their dance communication, but is it continually employed during flight? Our results indicate that path integration is weighted heavily when bees explore novel territory. On familiar ground, however, compass-guided flight vector instructions activated in a sequential fashion take precedence over the path integration system. In order to demonstrate path integration of foraging bees during long-distance orientation, the animals must fly "voluntarily" to a site that fulfils two simple prerequisites. (1) No landmarks visible from this point must indicate the direction of the hive, nor may the hive be directly visible. (2) The bees must have reached this point by a route that is not the straight line connecting the hive and the point in question. If animals manage to steer a direct course towards the hive from a place that meets these conditions, they must have estimated it from the length of path segments, and angles between these segments, flown prior to arrival at the particular site. To ensure condit ion (1), we established one Langstroth hive box containing a populous colony of European honeybees