The condensation is formed when there is too much of a temperature difference between the air in the test tubes and the glass exposed to the outer air.
Since that night I've bundled the tubes under a heavy towel, making sure the front cotton swabs are still exposed to allow for fresh air, and this seems to work although I still do see a bit of condensation at times.
This got me thinking about how I could improve that airflow with the hope that the inner and outer temperatures could remain fairly equal and avoid any condensation. I thought that a fine wire mesh might do the trick. I have both 150mm and 200mm test tubes and looked around for something that I could use as a cap into which I could insert the mesh. I managed to find some bottle inserts used to restrict flows (such as those in a bottle of Soy Sauce) that not only fit, but could be used for BOTH sizes of test tubes. The wider test tube snaps tightly inside the cap outer rim\ while the smaller test tube fits into the plastic wedge used to create the block that restricts the flow of liquid. I was able to hot glue circular mesh cutouts on the 'top' of these plastic restrictors, and then cut out the plastic that blocks the flow (the pictures below showing one of these caps still with the plastic).
I have not used them yet but was wondering what others thought about it and whether or not this may be a bad idea. Would it be a problem to have the ants more exposed to the outside air like this?
PS: Before anyone asks, I do not know from exactly which sauce bottle these restrictors came from as these were in my 'parts bin'. I wish I knew since if they work out I'd like a to make a dozen more myself.