I put some wet frames in a 5-gal bucket and set it out for the bees to clean. I looked at it late last night and there were still bees on them. Early this morning, just before daylight, they were still there. I had always thought that if the little critters didn't get back inside the hive at night that they were doomed. Apparently not. I noticed the same thing with ferals up in the mountains in that they would be hanging on a flower all night until they warmed up a bit in the morning and started moving. Now I'm wondering just how tolerant of low temperatures bees are, and whether the clustering and temp control inside the hive is for the benefit of eggs and larva and not necessisarily critical for the adult workers.