We've seen strange swarm behavior here in Southern California the past two years. Anecdotes follow:
Last year, we had a swarm that probably lost its Queen (or didn't have one to begin with). They maintained a big ball in the tree for nearly four months, gradually all dying off. They made no honeycomb, just a few weird strands of propolis. In the past, when swarms failed to form a new hive, they didn't continue to go and harvest pollen and function like a hive, but all died off much more rapidly.
This year, we had a swarm ball up in a tree mid-afternoon. They hadn't found a hive by the next morning. By the next evening, they were all falling to the ground and writhing as if poisoned or something. By the second day, there were just heaps of dead bees all around the garden.
I don't claim to be any expert (although my Dad kept several hives when I was a kid). Still, I haven't seen this before. I don't know the cause of either phenomenon.