If we don't see you posting anymore we know what happened.
So these bees were going behind the chimney? Were you able to detect them from outside with the Fluke Thermal imager?
Hopefully these bees aren't in cinder blocks like the last wall I opened up and they were inside and the owner not wanting to cut into it due to structural support.
Jack, no the Infrared does not work thru stone or brick I've found.
In this case the bees are going in at the corner of the brick chinney chase and are actually in the wall above the fireplace mantle (new photos at link). I'm going to have to remove them from inside the house. I'll post up the pictures, but it's going to be awhile, I've got 4 jobs ahead of him.