The horned osmia, one of the wild bee species found throughout Europe.
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/ The bee pampers
There are a thousand species of wild bees in France, but all of them are much less well known than the European honey bee, which produces honey.
However, these wild bees also provide many services to nature and are equally threatened.
A good reason to offer them a shelter in your garden or on your balcony?
This is what Bee-Home offers in France, by delivering nesting boxes sold with the first cocoons ready to hatch.
Bee pampers go even further by setting up a monitoring of nests that remain for long months at the mercy of predators and parasites.
One way to strengthen populations?
They live alone, do not make honey, do not sting, are not interested in our food.
For all these reasons, wild bees are much less well known than their cousins, the honey bees.
However, in France, "there are nearly 1,000 species of wild bees when there is only one honey bee, the apis mellifera", indicates Lise Ropars, ecologist specializing in pollination at the Institute. Mediterranean Biodiversity and Ecology (IMBE).
Like the servants, the solitaries work on pollination, so essential for the reproduction of a large number of plants and flowers (see box).
They also face the same threats: pesticides, urbanization, parasites.
In her garden, on her balcony or on a window sill
Lise Ropars still does not put the domestic and wild bee on an equal footing: "By its production of honey, the former has a strong economic interest for humans and is therefore very well maintained," continues Lise Ropars. .
It will last over time despite the pressures.
This is not the case for wild species, for which the risk of extinction is real for some.
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A good reason, then, to welcome a nesting box for wild bees at home?
This is what the Swiss company Pollinature has been offering with BeeHome, in France, since 2018, or even the Dorloteurs d 'bees, a project launched in March 2020 by the La Rochelle company "A roof for bees".
In both cases, their nesting boxes are wooden playhouses, similar to the insect hotels that have been popping up everywhere in recent years.
Particularity: they consist of tubes like so many hollow stems, the preferred natural shelter for a large number of wild bees to build their nests.
You might think that a pile of dead wood left at the bottom of your garden would do just as well *.
Pauline Jung, head of development at Bee Dorloteurs, agrees.
“But these natural shelters are becoming scarce as hedges, embankments, vegetated meadows disappear,” she recalls.
The advantage of our nesting boxes is that they can be placed in a garden as well as on a balcony, or even a window sill.
And as much in the countryside as in the city.
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Cocoons sheltered in winter
Above all, even if your pile of branches ends up hosting a nest, there is nothing to say that this will result in a new generation hatching the following spring.
Ensuring offspring is an obstacle course for wild bees, which devote most of their short lives to it.
Six to eight weeks for females, and only a few days for males.
They have to build their nests, lay their eggs, then hope that they turn into larvae and finally into cocoons, two stages that take place when they have already ceased to live.
"For many months, the nests are at the mercy of predators and parasites", summarizes Pauline Jung.
In a way, Bee Pamperers and BeeHome are forcing fate.
Their nesting boxes are delivered with the first cocoons ready to hatch.
BeeHome stops there for its offer to individuals.
Les Dorloteurs go further, with a subscription system that allows tracking over time.
“From March to the end of August, the different species of wild bees will lay their eggs in the tubes, which they will stop up with a cover of earth,” says Pauline Jung.
We then ask our subscribers, a little before the fall, to remove the blocked tubes from the nest box and place them under a protective net.
Then, before winter, to send us their cocoons.
We then clean them of their parasites and store them in the right temperature and humidity conditions all winter ”
3,239 nesting boxes distributed for pampering people
The following spring, the cycle begins again: the healthy cocoons are returned to the sender and the surplus, when there is any, is given to new subscribers, in the hope that new populations will hatch.
In one year, the Dorloteurs have already swarmed 3,239 nesting boxes in France, while BeeHome has counted 10,000 in France since 2018.
What to strengthen the populations?
Lise Ropars has some reservations about this type of initiative, "when they consist of delivering cocoons that come from the same gene pool".
"The risk in the long term, if the practice becomes widespread, is to standardize populations, and potentially to weaken them," she points out.
Build a library of cocoons with subscribers?
BeeHome does not hide it.
The wild bee cocoons they deliver come from its own populations, which it has been developing since 2013. “But we are very careful,” assures Chloé Humbert-Droz, development manager at BeeHome.
Our populations already remain wild, multiplied outdoors, which makes it possible to maintain genetic mixing.
We also only work with species naturally occurring throughout Europe, and we only ship very small quantities each time [25 cocoons].
Interaction with the populations already present on the spot is therefore minimal;
it even brings positive genetic diversity.
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For their part, the Bee Pamperers have another approach.
“In 2020, for our first year of existence, we have chosen to send the nesting boxes without cocoons,” says Pauline Jung.
The bet was twofold: that local wild bees make their nests naturally in the tubes and that our subscribers play the game in us trusting them for the winter.
It worked rather well, since the Dorloteurs collected 20,000 cocoons for the first season, thus allowing to fill new subscribers.
“While respecting the geographical origins, insists Pauline Jung.
A cocoon that was sent to us from the Lille region left for the same place.
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* "All the same, making sure that these hollow rods are less than 8 mm in diameter to protect the nests from parasites", advises Lise Ropars. She specifies that a small pile of soil can also be very suitable for solitary bee species used to nesting in galleries.
The wild bee, the orchard's best friend?
Wild bees do not have the same technique as domestic workers for collecting pollen.
In the latter, it is mixed with nectar and saliva and stored in small baskets at the level of their hind legs.
“Wild bees, which must stay away from their nests for as short a time as possible, are parents in a hurry,” explains Pauline Jung.
They fix the pollen grains to the hairs they have in the abdomen, resumes the member of the Pampers.
They certainly capture a lot, but also lose more easily on the way, which benefits the flowers they visit.
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What makes it a valuable aid for orchards?
"They are in any case very complementary to honey bees, very often used today by fruit producers, but which nevertheless quickly come up against their natural limits," explains Chloé Humbert-Droz.
Unlike domestic workers, wild bees such as masons will only go to fruit flowers, tolerate cool and rainy weather much better…
And the fact that they are close to their nests
allows pollination to be targeted.
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All that was needed for Pollinature to launch Osmi Pro, an offer addressed to fruit producers (mainly apples, apricots, pears, cherries, strawberries, etc.) and which consists in selling them, in the spring, mason bee populations with nest maintenance.
The service has been around since 2013, but the Swiss company opened it in France only last year.
“In 2020, we helped pollinate 200 hectares of fruit trees,” says Chloé Humbert-Droz.
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