Found another bee nest in the same log as the ones
. This time the poor mother didn't leave right away so I had a chance to snap a couple of pictures of her.
This nest was under the bark that was loose and easy to rip. There was a lot of frass and debris that the bee used to build the cells. (Added:8/4/07)
The log where I found these nests:
An abandoned nest found in winter, there are some remnants of pollen: