I added a home made screened bottom board (SBB) to the hive on the left today. The hive on the right has a normal solid bottom board. I took the photo around 8:00pm (about five minutes ago) after a hot day.
It could be a coincidence, but if I were to judge only from the photo, I’d say the bees on the right live a hot and humid hive and the bees on the left are chillin’. I wish I had the materials to build an SBB for the hive on the right.