Preparation of the pollen loads

The preparation of the pollen loads will be carried out as follows (see Delaplane et al., 2013a and Carreck et al., 2013 for more information):

1) All bees from sub-sample A are kept on a deep frozen metal plate (≤ -18 °C).

2) The pollen loads will be detached from the legs of the forager bees and placed into a vial.

3) All pollen loads from sub-sample A will be collected and pooled in order to get at least 100 mg of pollen for residue analysis. If < 100 mg is obtained from sub-sample A then sub-sample B will be prepared. If this is the case, all bees of sub-sample B will be prepared in the same way as sub-sample A and added to sub-sample A. The total number of prepared bees and the sub-samples used will be recorded.

The pollen samples will be unfrozen during the preparation of one sub-sample. The bees and pollen will be transferred back to the freezer immediately after the preparation of one sub-sample. Each sub-sample will be labelled 3 times and will include at least the information given below. All samples will be frozen at ≤ -18 °C outside of the sample preparation time.