Fig. 3. Search density distribution of the ants' nest search behaviour exhibited under different training and test conditions. Control 1: ants were trained and tested without any landmark. Control 2: ants were trained with a landmark located at the nest entrance but tested without one. Test 1A: ants were trained and tested with a landmark at the nest entrance. Black square, position of landmark; dotted line, position of path-integrator-defined nest.