RE: aggregating Megachile and nest site longevities
Folks- in fact Osmia and Megachile do aggregate on occasions, but typically the ground-nesting species (or any for cavity nesters, if available holes are also aggregated). Attached is a paper reporting a case of the former.
As to longevity of nesting aggregations, the longest yet known is ½ century, with a summary in this other paper of mine on alkali bees (which rounds up both published and validated pers comm. sources).
In the event that the attachments don’t post, Sam and I will work out a way for you to get them.
James H. Cane
USDA-ARS Bee Biology and Systematics Lab
Utah State University, Logan, UT 84322 USA
tel: 435-797-3879 FAX: 435-797-0461
Gardening for Native Bees: http://extension.usu.edu/files/publications/factsheet/plants-pollinators09.pdf
"The obscure takes time to see,
but the obvious takes longer"
Edward R. Murrow