Fig. 1. Results of experimental Series I carried out in the AWBFF (indoor) at the Australian National University. A pair of blue/white gratings oriented at 45° or 135° to the horizontal was used at the feeder and the hive. The results indicated that trained bees can reverse their pattern preference following midday breaks, as well as an overnight break, both at (A) the feeder and (B) the hive. The modulation of the average choice frequency, with reference to 45° grating can be approximated very well by a sinusoidal curve with a frequency of 0.52, i.e. a period of 12 h. The correlation coefficient are 0.98 for the feeder and 0.998 for the hive, respectively. Terminology for the test types: M, morning; A, afternoon; H, hive; F, feeder; 1, early; 2, late. ^***P<0.001. See text for further details.