Fig. 1

Diagram of experimental design. Diagrammatic representation of the experimental design within each Region. In each of the periods (Before, During and After) in each of the first 4 years, there were usually several assessments, made on different dates. Details of the assessments are summarised in Table 1. The dark grey horizontal lines show how the same 12 hives were employed throughout the experiment (except when a colony had to be replaced because it died out—see Pilling et al. [5]). The lighter grey vertical columns indicate the overwintering periods between years