It isn’t a very common habit, but a few Osmia bees actually nest in snail shells. The best known species are European, like Osmia bicolor, described in this link (written by BugGwen who writes for Wired Science), with wonderful embedded videos. Bees that nest in snail shells are not common in Canada. In fact, as far as I know, the only species is a little blue one called Osmia conjuncta. This bee is incredibly common at our research sites in southern Ontario, but so far, seems to have been found nowhere else in Canada. I keep trying to find nests, but despite collecting hundreds of land snail shells, I’ve only found a few shells with dead bee occupants.