Fig. 2.

Homing flights and homing points of the three test groups. (A–C) Shown are 35 examples of homing flights of SF bees (A), VF bees (B), and R bees (C) tested with the normal arrangement of the tents. The homing flight component of the full trace was detected by using the algorithm described in Materials and Methods. The bees in A and B were released at different sites around the hive, and those in C were released from three release sites in the southeastern to southern part of the study area. The final flight path of each bee is shown with a different line. Flight traces in A and B were recorded in the first study period, and those in C were recorded in the second study period. Because R bees performed very short search flights, and because they were released in the southeastern to southern sector close to the southern groups of tents, it is not surprising that their homing flights are close together. Notice that the borderline was located 50 m to the east as compared with the first study period, and bees did not follow the borderline when homing. (D–F) Localization of homing points for the three experimental groups: SF and VF bees, first study period, normal tent arrangement (D); SF bees, rotated tent arrangement, first study period (E); and R bees, second study period (F). In F, the stars mark the homing flights of R bees under sunny weather conditions, and the crosses indicate those under an overcast sky. The homing points were calculated by using the algorithm described in Materials and Methods. The test with the rotated tents (E) proves that landmarks on the ground are sufficient to allow homing. Notice that most homing points are within the visual range of the tents when the tents are arranged normally, but very few lie close to the tents when they are rotated, indicating that the tents play a role in localization. The results from R bees under an overcast sky show that homing does not require the sun compass.