Ant toilets.

21 plaster nests which had been inhabited by 150–300 Lasius niger workers for 2 months. Dark coloured patches (= toilets) can be seen in every nest. The colour of the patch corresponds to the colour of the sugar solution the ants were fed. High resolution images of each nest and the surrounding foraging arena, and images taken throughout the course of the experiment, are available from the Dryad Digital Repository: http://dx.doi.org/10.5061/dryad.[doi:10.5061/dryad.9fs7n].