Among pollinating insects, next to osmias, there are megachilis. We are always in the large family of solitary bees, which in turn is part of the superfamily of bees (where there is also the apis mellifera), but megachyls are different from osmias and also differ a lot in habits. So if we want to build a shelter for these pollinating insects we have to think of one that is a bit particular.
Much tells us the fact that bees of the genus Megachile are also called 'wallpaper bees' or 'leaf-cutting bees'. This is because they have the habit of covering the inside of the nests with portions of fresh leaves rolled in the shape of a cigar. Inside these well-lined tunnels, the Megachili overwinter at the larval stage (unlike the adult overwintering osmias) and only come out at the beginning of summer.
Therefore a refuge for these pollinating insects it must have a blind bottom cavity with a fairly large diameter, larger than osmias. A good idea to give shelter to all the solitary bees can be to build a single shelter by placing different sections side by side, as if it were a hotel with different types of rooms. The ideal are sections of logs with holes drilled using bits of different sizes. Or pieces of bamboo canes of different sections, after having plugged one of the two ends.
With an insect shelter of this type we will have available pollinating insects very effective in the vegetable garden and in the garden, and it will happen that the osmias will naturally occupy the smaller cavities while the Megachili the larger ones. We will soon realize this thanks to another difference: the Megachili usually close their nests with a sort of door made up of small pieces of leaves, while the osmias usually do not. Looking at the entrances to the tunnels of our bug hotel we will understand who we are hosting.
If you don't have time to build your rrefuge for solitary bees, do not worry. Online you will find some different and well-made ones at an affordable price, with home delivery.
Basic solitary bee shelter
Shelter for solitary hive-type bees
5 star solitary bee shelter