The pollinating insects they are the ones that fertilize the flowers from which the fruits develop. Welcoming them well in our green space is useful as well as for predatory insects, which instead help us fight infestations. A balanced presence of pollinating insects and predatory insects is important for healthy organic cultivation in the vegetable garden and in the garden.
The presence of profits pollinating insects, as well as predatory ones, it can be consolidated for example with a bug hotel, a shelter for insects. Just know that every species has preferences, even in terms of accommodation as well as diet. For the pollinating insects we will therefore need suitable shelters, which we can also build ourselves.
What are pollinating insects? The main ones are bees and butterflies, then there are some beetles and some diptera which, however, will be less interested in bug hotels because they overwinter in the ground. So let's focus on welcoming bees and butterflies, and try to understand well which insects we are talking about among the many there are.
The superfamily of bees, Apoidea Hymenoptera, includes about 20 thousand species. Of all the best known is the domestic bee, Apis Mellifera, but it's not her we're talking about. The most important bees like pollinating insects are the so-called solitary bees, which belong to different families (Colletidae, Andrenidae, Halictidae, Mellitidae, Magachillidae, Antophoridae, Apidae) and that in Italy they have been observed in 960 species.
The journal Science has published an article with the results of a study conducted on 41 crop systems of all continents which show the primary role of solitary bees as pollinating insects. They are even more effective than their domestic cousins in a limited range of action (the maids go further) and their function cannot be replaced by the introduction of hives. In practice it is said that, for the pollination of a vegetable garden or an orchard, a bug hotel for solitary bees is more effective than a beehive for domestic bees. Except for honey of course.
To house solitary bees, shelters are the same as those that can be built for solitary wasps (or mason wasps) which are predatory insects. The ideal are pieces of log with drill holes of different sizes. Or bamboo canes, common canes or grass stems of various diameters. The important thing is that they are hollow corridors with a blind end, 12 to 20 cm deep and positioned sheltered from wind and rain. It is important that the tunnels also have a minimum slope to let the rain flow.
Of solitary bees (osmias and Megachili) as well as solitary wasps, you must not be afraid because they hardly sting and only if disturbed. To understand if a shelter is occupied by a solitary bee or a solitary wasp, look at the closure of the nest: the opercula made by bees remain at the same level of the plant material, those of the wasps instead protrude from the surface of the shelter and are colored clearer.
As beautiful as they are dangerous. The adult forms of most Lepidoptera, butterflies and moths, are pollinating insects, but in the juvenile forms of larvae and caterpillars they can be insatiable devourers. The box borer, the infamous boxwood defoliator caterpillar, is also a beautiful butterfly in adult form, but in the development stage before flickering it can burn a hedge in an amen.
Beware then: if you want to host butterflies to see them flutter colored on the flowers, where they will perform their function of pollinating insects, expect to find some unwelcome caterpillars on garden vegetables. And know that you will please the birds, which are known to feed on caterpillars.
Hosting butterflies in the vegetable garden and in the garden is more a tribute to biodiversity than a need for pollination, which is best done by bees. That said, if you want to build a butterfly shelter you need a sheltered cavity (like a wooden house) protected by a wooden door equipped with vertical slits (to allow the insect to enter without damage to the wings.
If you want a solitary bee shelter and don't have the time to build one yourself, you can buy one online: