Overnight vibrational amplitude distributions for three colonies.
In colony No. 5, the most common vibrational amplitude oscillates regularly over the entire summer, whilst in colony No. 6, a period without a peak in May takes place three weeks after the primary swarm (the date of which is indicated with the yellow tick in early April). Visual inspection revealed that colony No. 2 was temporarily 'drone laying' in July, and this is also reflected as a clear perturbation of the cycle. Histograms are all normalised to their maximum (red pixel). The data for all colonies is available in S1 Fig.