Among pollinating insects that might harbor in your insect shelter there are osmie. It is a genus of solitary bees, that is, those that do not build the hive and do not produce honey, of which there are about 300 different species.
Osmias do not produce honey but are very good at pollinating, even more than their cousins domestic bees when the range of action is not too extended. A vegetable garden or a garden make up their perfect environment and this is where they give their best like pollinating insects. That's why I recommend creating a bug shelter for them.
Characteristic of osmias is the marked difference between males and females. The former are smaller, covered with white hair on the head and equipped with longer antennae. The females are larger and more robust, equipped with collector bristles for collecting pollen: in the family they are the ones who do the real work of pollinating insects. Males do not pollinate, they visit flowers only to feed and serve for reproduction.
Osmias are solitary animals, but they have the habit of nesting in a gregarious way. This gives us a first indication of how our osmia shelters should be built. Refuges that will be used by us to ensure pollination in the vegetable garden and garden, but will also be used by osmias to survive. The lack of suitable places for reproduction is in fact the main cause of the worrying decrease of pollinating insects and of solitary bees in particular.
A second indication on the construction of the osmia shelter is provided by the reproduction modality of these hymenoptera. After wintering, the males are born first in spring and wait for the females just outside the nests. The coupling of osmias does not occur in flight, as others do pollinating insects, but on the ledges and on the vegetation near the nests.
Putting this information together, we can have an idea of how to build a nest for osmium, or how it should be what we will buy. As with all solitary bees, osmias need a nest with hollow, dead-end corridors. The diameter of the corridors can be between 4 mm and 12 mm, the length varying from 12 to 20 cm. To encourage reproduction, the entrance to the nest can be enriched with vegetation, small brambles and rolled up stems, and the nest itself can be hung near shrubs and bushes that function as a support.
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