It’s very interesting to watch their comings and goings.
We seem to have some uninvited, though not necessarily unwelcome, guests taking up residence in the outside wall of La Petite Maison.
We noticed a couple of bees buzzing around the house yesterday, and on closer inspection they were busily flying in and out of these little holes in the south-facing end wall. I assume that the holes must have been drilled to fix something to the wall in the past, but they are now clearly very attractive to these bees.
We think that they are red mason bees, but we’re happy to be corrected if anyone knows better! In any case, they are obviously solitary bees, which are not aggressive, and do not swarm, so they are very welcome to make their homes in our wall. Hopefully they will repay us by pollinating our flowers, fruit and vegetables throughout the spring and summer.
750 metres 
It looks like an Osmia cornuta to me, you don’t get these in the U.K. They are known as very good pollinators but they have a very short season and will be finished quite quickly. On the other hand as you have got a very attractive wall you may see other bees nesting there. Amelia