The colony in Hive B has failed or absconded. The hive is now completely empty.
The colony has always been small. In a year they built only 5 frames of comb (on National deep frames). I thought that maybe the effort of being at height had over-stressed them so I moved the colony from the out apiary to my back garden. I placed them under an apple tree in the hope that they would recover. There is good forage and they were at ground level.
I had seen some coming and going at the hive entrance in recent weeks. It all looked like normal activity. I saw no wasps going in or out. The entrance was partially concealed by apple tree leaves so I thought the colony was ok. I didn't open it.
The position under the apple tree may have encouraged robbing by wasps which I hadn't noticed. The colony may have lost its' Queen. It may even have been the move which killed her - although I was gentle.
Whatever the cause, I noticed unusual activity at the hive entrance yesterday. I checked the removable base board and saw a large amount of sugar on it - clear evidence that there was robbing of crystallised honey. Today I opened the hive and found it utterly empty: no bees; no Queen; no brood; no stores. I have no idea where the Queen and the other bees went.