Fig. 6. (A) The natural alley formed by plants that had grown in the furrows used in the previous year to mount the walls of the channel. (B) The trajectories of ants passing through the natural alley. In the box-plot representation, the orange line marks the position at which the left and the right rows of plants appeared to subtend equal visual angles. Since the number (29 in the left row and 23 in the right row) and the linear heights (0.13±0.06 m in the left row and 0.18±0.07 m in the right row; means ± S.D.) of the plants varied between the left and the right sides of the alley, the orange line represents only an approximate mean value. Nevertheless, the ants’ trajectories are shifted towards it (see text). Red line, midline of alley. N=19.