Got home about 5 pm on Thursday and found a softball size cluster hanging on the bottom of an empty hive in my back bee yard. Put out a plywood nuc (just happened to build a few a week ago for splits next year - I encourage all my fellow newbies to get a few cheap nucs with extra frames "just in case") with 5 empty frames, sprayed one of the frames with light syrup scented with lemongrass, and the cluster entered within a minute. Gave them a frame of honey as per the advice of my mentor, and they've gone through 2 jars of syrup in just a few days. The bees just fell in my lap .
Checked another hive (in the front yard) yesterday and found 5 swarm cells, 3 open and 2 still closed... so I think I found the source of Thursday's little swarm. Surprised they swarmed given all the space they have (2-10 frame deeps and a 10 frame medium... deeps are packed but they're not doing much with the medium) and that I just started that colony from a package at the end of April. Still a ton of bees in hive. Feel fortunate to have caught the swarm.