Bee Hotel - Nature Notes

Three years after I first wrote about the 'bee hotel' I thought it was time to produce an update.

The 'bee hotel' is a construction, actually several, that I have built in order to attract and provide nesting sites for a variety of bees (and also wasps) that nest in holes in wood or other materials. While many species nest in the ground many others use either natural holes in timber, such as those made by wood-boring beetles, or excavate their own in rotten wood.

My original one was sited against a wall facing roughly SSE so it catches the morning sun and warms up quickly. Having the nest holes facing the sun is essential here in central Wales where it rarely gets warm enough to raise the temperature of the nest sites high enough for the development of the bee larvae unless they receive direct sunlight. Being against a wall means that once the wall has warmed up it radiates heat back even if the sun has gone in. I have built another 'hotel' and sited it in our orchard to provide pollinators for the apple trees, as no wall was available I included a concrete slab in the design to provide some thermal mass to help on cool days.

The idea of encouraging wild bees has become much more mainstream in recent years as concern about their status has increased. Where we live honey bees do not thrive, partly due to climate, but also to the total destruction of natural habitats by agriculture. So we have been encouraging wild bees to do our pollination since we moved here 17 years ago.
I have been in contact with a Romanian scientist and blogger László Zoltán who is trying to educate and encourage Romanians to protect their wild bees. There they still have much low-intensity agriculture but things are changing. His blog is at http://think.transindex.ro/?cikk=26542 (in Hungarian, but with photos).
While I was in Provence earlier this year I was encouraged to see some artificial bee nests in almond orchards, although on a very small scale. It turned out they were some early experiments by a researcher and the farmer. The year before several hundred honeybee hives a short distance away had been wiped out by insecticides sprayed in peach orchards. With the almond crop entirely dependent on insect pollination they were looking for alternatives to honeybees and the risk of losing them, and therefore the crop, due to the actions of others.

Bee tubes in an almond orchard.

Numbers and species in my "hotels' fluctuate from year to year, due in part no doubt to weather conditions, possibly also to the natural cycles of parasites and hosts. Over the years several new species have turned up, while others have only appeared in some years. The species list of bees, wasps, and (one) ant using the 'hotel' currently stands at 20.

Bees

Chelostoma florisomne
Coelioxys inermis
Megachile willughbiella
Megachile centuncularis
Osmia caerulescens
Osmia leaiana
Osmia bicornis
Stelis phaeoptera

Wasps

Ancistrocerus parietinus
Passaloecus corniger
Passaloecus gracilis
Dipogon variegatus
Sapyga quinquepunctata
Symmorphus bifasciatus
Trypoxylon figulus
Chrysis ignita
Chrysis mediata
Trichrysis cyanea
Chrysura radians

Ant

Leptothorax acervorum

The Osmia bicornis females seem to have a clear preference for using the blocks of oasis, the type used by florists for arrangements of live flowers. The bees excate their own nest chambers in the blocks, hollowing them out completely in one season, and filling them with stacks of mud cells. So new blocks need to provided each Spring alongside the old before the bees emerge. They will also nest in very rotten wood where they also dig their own chamber, so the oasis is presumably a substitute for this. All sorts of pre-formed holes and cavities are used as well, where they do not need to do any excavation, the considerable extra effort required to dig out their own holes must be worth it though.

Male Osmia bicornis at a nest in a block of oasis.

Several of the species are cleptoparasitic or cuckoo species, laying eggs in the nests of other species without doing any of the work in provisioning. A rare species that is present here is Stelis phaeoptera. The females are always around the 'hotel' looking for nests of their hosts Osmia leiana. Perhaps in response to this it is noticeable that many fewer of the Osmias have nested there in recent years, spreading their nests much more widely around the garden and surrounding area.

Only a couple of years ago there were no modern books on wild bees at all, other than bumblebees. Now with all the renewed interest and publicity there are several in English, and this year also an excellent book (in French) by Nico Vereecken. Nico is also a superb photographer and the book contains lots of his photographs, and a few by others. His book "Découvrir et protéger nos abeilles sauvages" is available in the UK from Amazon (though possibly other sites as well).