Beautiful idea with a beautiful design from mitrasmit on Thingiverse:

The bees are in trouble. Toxic chemicals, diseases, and a decrease in suitable habitat threaten their existence more and more. There are many types of bees, of which the honey bee is the most well-known. But did you know there are many other species that live in solitary? They don’t have a beehive and live in their own little hole in a piece of wood, stone, or earth. Depending on their size, they want tunnels between 3 and 10mm in diameter, with a length up to 150mm. They use it throughout the seasons: hibernation in winter, shelter in autumn, nursery in summer and spring.