Figure 4: Activities observed at 28 nests (four batches) of Halictus scabiosae nests over three days (1–3). (a) Irradiance in lux and (b) ambient temperature in C° measured in the shade. (c) Out-flying and (d) incoming activity pooled over all 28 nests; data were normalized per nest and 30 minutes of observation time; red curves show the regression functions, which allow to extrapolate the flight rates before the start of the observation sessions (which are coded by the grey background; am, bright grey; pm, dark grey); (e) sealing activity at the study site, given by the number of sealed nests in steps of 30 minutes; (f) the impact of nest parasites (for measurement, see Methods) on the experimental nests of H . scabiosae, given by the number of parasites per nest and 30 minutes of observation time. The regression curves (red) refer to all means coded in black columns which are used for further analysis (for equations of the regression functions see Tables 1 and 2 and text).