I spent two months (June and July) in my home town in Baja California, where I met an unconventional beekeeper. He has a small apiary of colonies (never treated) that he rescues from buildings, but his favorite colonies are actually located in nature (more than 200 sites!). I know they can live in rocky crevices, buildings, etc., as most of the ones I saw, but I was thrilled to find some under the ground in rabbit burrows!!! Some of the Baja California chaparral area by the Pacific Ocean coast has no trees nor boulders, so they have not so many other cavities to build their nests than those built by mammals in loose ground. I guess they use lots of propolis to cover the walls and provide support to honey combs.