Terry,
Yes, there are designs of nest structures available. My reference
material is rather limited but perhaps Chris Plowright at U. of Ottawa
can provide more uptodate info. Also, Phil Torchio at U. of Utah may
have quite a bit of info available of nest designs for non-Apis
pollinators (not limited to bumbles).
In addition to the actual placement of 'bait' nesting sites, undisturbed
vegetation surrounding cranberry fields are equally valuable. Flooding,
use of pesticides, clearing of vegetation, and other disruptive
activities have been the primary causes for the quantitative decline and
diversity of wild bee species.
Paul van Westendorp [log in to unmask]
Provincial Apiarist
British Columbia