We have been watching a strange gathering of large wasps on a single rose-leaf just in front of our outdoor dining table the last few days, up to ten wasps at the same time, and we have been wondering what they are doing there. I tried to get close to them, but they didn't like it when I lifted a leaf above them to get a better view this morning, so they flew away, but now some of them are back again. There does not seem to be anything on the leaf, but they still seem to be eagerly licking. The leaf above had some small markings that showed that there must have been some other visitors earlier, maybe aphids? which have secreted some sugary liquid that dropped on the the leaf underneath. I am pretty sure they are paperwasps, Polistes dominula, the photo is not very good, but the antennas are clearly orange in some other pphotos. Do you have any other more likely explanations for this gathering?