How to make a house for wild bees (also in the city)

Today May 20 is the World Bee Day. The United Nations Organization highlights that human beings depend on the survival of bees, which, along with other pollinators, such as butterflies, bats and hummingbirds, are increasingly threatened by human activity.

Pollination is essential for the reproduction of many crops and wild plants. Nearly 90 percent of flowering plants and 75 percent of food crops depend on pollination. In addition the pollinators They are essential to maintain and enhance biodiversity.

The goal of World Bee Day is to protect bees and other pollinators so they can contribute to solving problems related to food supply in the world and end hunger in developing countries.

Bees are at risk of extinction

Bees are so familiar to us that we are not aware that they are threatened. Thirty-five percent of invertebrate pollinators, particularly bees and butterflies, and 17 percent of vertebrate pollinators, such as bats, are threatened with extinction globally.

The bee population has decreased worryingly, due to intensive agricultural practices and monocultures, changes in land use, pesticides, pests and climate change. The situation requires that measures be taken in all affected areas, starting with agriculture, but there are things that anyone can do regardless of whether they live in the country or in the city.

How to build a shelter for wild bees

Wild and solitary bees like to find safe and sheltered places. We can help them by building adequate shelters; in fact, some stores sell “hotels for insects”. However, not all of them work.

As Jesús Quintano, naturalist and consultant in biological control and biodiversity conservation in agroecosystems, explains, in order for “wild bees to nest in our bee hotel, we must take their nesting preferences into account. What they are looking for most are long, cylindrical holes.

In nature they use the canes and herbaceous stems that break, or they opt for weakened or dead trees, where the beetles that feed on the wood leave galleries that they later occupy. So, we must use materials that offer these spaces, such as hollow reeds, drilled wood, drilled mud bricks…”.

Quintano warns that materials that do not have a tubular shape are not appropriate (pineapples, wood chips, mounds of stones…). He also recommends a little trick if using wooden dowels: “Drill them on the side perpendicular to the grain, leaving the faces where the rings are visible above and below. This will help the fibers curl less inside, especially if there is humidity”.

Materials and size of the holes

Reed canes are suitable (Phragmites australis), dry thistles, fennel… “The corky pith will be pierced by species belonging to the genus Ceratina,” says Jesús Quintano.

As for the diameter, if it becomes excessively large, “no bees will nest, so we must avoid bamboo, which is very wide.” should be situated between 2 and 10 mm, “being his favorites those that go from 4 to 8 mm”. As for the depth, he recommends 15-20 cm. “All this can also be done with hardened mud or clay bricks”, concludes the naturalist.

How to protect the nest of bees

On the other hand, we must create a refuge that is well insulated and protected from water. That is why it must be sheltered and treat the nest with virgin wax or oils.

A good idea is to give the nest some color, especially blue or purple, to attract the attention of the bees. We can paint the front of the house or the outline of the holes in these colors. Can be painted with a natural dye based on gentian violet, which is also a powerful fungicide that will protect the house from bees.