Fig. 2. Schematic representation of the position of the nest (N) as defined by the path integrator (PI-position, open arrowhead) and as defined by the ground landmark (LM-position, filled arrow) in the different sub-sets of experiment 1. During training both positions coincided, but in the test situations the LM-position was usually shifted away from the PI-position towards the point of release (R). This decoupling of PI-position and LM-position ensured that within the test channel the ants encounter the landmark before they have run off their home vector, i.e. before they have reached the PI-position. F and open square, feeder in the training channel; filled square, point of release in the test channel; N and filled circle, nest in the training channel; heavy bar, ground landmark.