I know they swarm periodically. We have them once or twice a year here... This spring, we were in the garage & my wife said she heard bees. I walked outside & saw that the whole front yard was a swarm (no, I'm not exaggerating)... We closed the garage door & went in the house till they settled down (the queen landed in the live oak 25' from our front window). They moved on about 36 hrs afterwards.
From past experience, I can tell you that they are not aggressive while swarming, but they are down right nasty to live with once they establish a hive & have honey/young to protect.
