While digging through alot of trees over the summer looking for these nests ive noticed that the bees have a few different kinds of nest formations. I have come across the type of formation you have photographed with the cells by themselves too. I dont know what it means, its possible the cluster nests i have photographed are the result of many bees working together since there were at least 3-4 bees present when i uncovered them. I think the pollen might have gotten squished from me damaging the nest while digging through the wood (it wasnt intentional) since these nests are very fragile while still in the tree. The nest i have that still have pollen inside has it stored in loaves. I'd imagine all a. pura store it like this.

This species is considered solitary. It is not known to be social and to work together. I keep scratching my head about these differences in nest construction and pollen ball structure. Do you have other images of the pollen balls and the cells? You can e-mail them to me if you prefer and if it is convenient to you (Bmoisset_nospam@aol.com). I would like to ask somebody about this.

It keeps saying there is an error with the name Bmoisset_nospam@aol.com. Is there a space between Bmoisset and nospam?
If i cant e mail you i'll upload the pictures i took on here.

Delete that part -- a lot of people on BugGuide include something like that when they type their email addresses, to prevent spambots from collecting their real address.