I can’t remember if I told you or not, but last fall I had bees from one of my hives leave. Before we had left on vacation, both hives were doing well. I had inspected them a few days before we were to leave and both hives had a good amount of honey stored up. When we returned though, one hive was empty. No dead bees just no bees at all. Had I killed the Queen inadvertently when I did the inspection? Was it really a weaker hive to begin with and I hadn’t recognized the signs? Was this Colony Collapse Disorder (CCD)? I don’t know for sure, but several beekeepers told me it sounded more like CCD. Bees will leave the hive (or swarm)in the spring due to overcrowding, but bees that leave their winter supply of food for no apparent reason is a mystery to many beekeepers and scientists alike.
Source: Bee Update | The Blonde Gardener