Not for swarm traps, but hives during winter inspection.
Why at night? Thermal cameras work at daytime as well as they do during nighttime.
Thomas, all you need to see - a single bee bringing pollen (if have time - wait to see more to confirm)....there would be no confusion about scout bees versus foraging bees.
Well, we have to consider this fact - Thomas maybe actually looking for an excuse to buy a thermo-cam.
This simple idea avoided me somehow.