I've done a bit of reading about the swarm I captured, and I've come to the conclusion that I don't have a mature, fertile queen. What I've got in an as-yet un-mated Virgin Queen.
In the spring, when bees are preparing to swarm, the colony prepares a number of "swarm cells" into which eggs will be laid, that will develop into young queen bees. Usually what happens is that the existing queen flies off with about half of the colony, and then the first queen to emerge from her cell tears open the other cells, and kills the other queens. Once in a while, a young queen will not murder her unborn sisters. They'll be born, and as soon as they can, they'll fly away, to start their own colony. This is called an afterswarm, as opposed to the prime swarm, which contains the abdicating queen.
I've been referring to our swarm hive as the Gloriana hive, in homage to history's most famous Virgin Queen, Elizabeth I of England.
I was telling Robb about all my reading, and he suggested that the fleeing queen might be more analogous to Mary Queen of Scots. If she hadn't flown, the ruling queen would surely have had her killed.