Fig. 2. Walking orientation of P. americana males in (A) No wind + no pheromone, (B) wind + no pheromone and (C) wind + point-source pheromone. Arrowheads indicate the orientation of the cockroach at the end of the track in laboratory wind tunnel. The circle represents the release cage. Vanishing direction (angle from release point to point where the cockroach leaves the field of view of the camera) is displayed in the angular histogram to the left with the mean resultant length (r) associated with the mean direction (). Day 1, 17/4/03; Day 2, 22/4/03; Day 3, 22/4/03; Day 4, 7/5/03.