Fig. 7. Deprivation experiments. The upper parts of the frontal fields of view of the ants were obscured by a screen. Screen C (oblique heavy black line) was positioned 6.8m from F9.5 in the direction of the nest (N) (see Fig.4C). Assuming that the ant walks along its normal homeward course (y=-0.548x+7.206) from F9.5, the positions where the top of a chestnut tree drops out of sight behind the screen and reappears under the screen were calculated by advancing the position of the ant by a 5.0cm step along the x-axis. Horizontal bars indicate the top parts of individual chestnut trees (A.t.3–A.t.7; see Fig.3) that could not be seen by the ants on their homeward courses. (A) Paths of all runs tested. N=36. (B) Paths exhibiting a characteristic sigmoid bend, selected from A. N=22. (C) The remaining paths shown in A but not in B. N=14.