Bee Hotels for Solitary Bees
You may be wondering what bees need a hotel for, when they make their own hives. The truth is that many species of bees are solitary – the do not live in hives but instead construct their own nest. The main reason for this is because in these species every female is fertile and this would not make for comfortable communal living in a hive.
But the actual reason for bee hotels themselves is that solitary bees have more and more difficulty finding some existing small openings to nest - given that dead trees are taken away (instead of deteriorating naturally and giving food and shelter to lots of fauna), walls are renovated and the openings in them get closed, open farming bulidings and dry stone walls are getting rarer, etc.
It affects a lot of species, insects, birds, small mammals, bats, reptiles (like lizards) That said, many initatives exist now to preserve dry stone walls, natural nesting areas (such as Natura 2000 in the European Union), and to insert artificial nesting places in gardens, schools and newly-made buildings ^^