Anyone taking the dog-walking path left from the Court Lane Gate can’t miss the massed aerial activity around a partly pollarded copper beech trunk down there. From a central rot hole in a cut limb about 4 metres up a cloud of 50 to 100 bees circles restlessly. There’s nothing to worry about, though, these are tree bumblebees, and as everyone knows bumblebees are cute and cuddly and very docile.
When, in 1926, Winnie-the-Pooh was introduced to some bees nesting in a tree, E.H. Shepard made a terrible entomological faux pas by drawing bumblebees when, of course, he should have drawn honeybees instead. Only honeybees make honey, and although most live domesticated lives in hives, the occasional swarm escape sets up what can really only be described as a feral nest in a hollow trunk, or a rock cavity. His error was doubly troubling to British entomologists because bumblebees also didn’t nest in trees. They do now.
In July 2001 a ‘new’ bumblebee species to Britain was found in the village of Landford, Wiltshire; highly characteristic with its strong tawny orange thorax, black body and bright white tail tip, quite how Bombus hypnorum arrived on the edges of the New Forest is still a mystery, but once arrived it soon started to spread. It is now common throughout all of England, much of Wales and has started to appear in odd bits of Scotland. On the continent it occurs right up to the Arctic Circle; like many animals common on the mainland it just seems to have been kept at bay by the Channel, since the glacial retreat and rising sea levels after the last ice age about 15,000 years ago.
As well as its distinctive colour pattern, this new bee also shows a very unusual behavioural trait. Whereas most bumblebees nest low down, in the ground, compost bins, hollow logs or large grass tussocks, Bombus hypnorum has a tendency to make its colonies in tree holes. Since a new common British bee required a new English common name, “tree bumblebee” was the obvious choice.
Old woodpecker nests and tree rot holes are not the only nest sites in Dulwich. The Lodge House at the College Road entrance has two swift nesting boxes fixed up under the eaves to encourage these charismatic birds, but the early-rising tree bumbles got into one first. Eventually, the nest will wind down and all the bees will die off except a new cohort of queens (fertile females), mated, and storing the sperm they will need to lay the eggs when they found a new nest on their own from scratch next spring. These queens will search out dry sheltered nooks in which to hibernate. It’s at this point that the empty box can be cleaned out to discourage another colony next year. The house in Dovercourt Road can then have the small loft hole plugged too.
Having a noisy crowd of potentially stinging insects buzzing around the roof, or the airbrick, or the garden nest box, might cause some initial anxiety, but I offer the Bumblebee Conservation Trust’s advice if you find some tree bumblebees nesting close to you: consider yourself lucky, just leave them alone, and let them get on with it. But remember, they will never give you any honey.
Richard Jones is an entomologist and writer; luckily, his next book House Guests, House Pests (Bloomsbury, due October 2014) will include an entry on loft-nesting bees, including the cuddly Bombus hypnorum.