I swung the net over the plant. My companion dexterously wiggled the little jar under the bumblebee until it plopped in. She then had to manipulate the cap up under the net to close the jar and bring it out from the net. We peered at the bee, now buzzing frantically in its prison – aha, we said – “it’s a buff-tailed!” How did we know? Because we had just been attending the lecture by Dr Nikki Gammans, of the Bumblebee Conservation Trust organised by Kent Wildlife Trust at Tyland Barn. We released the bee and went in search of others.
We had to learn to distinguish males from worker bees. Nikki helped us catch one and said she knew right away it was a male because of its lazy behaviour. Males only have to feed themselves and lurk looking for queens for all two weeks of their lives. Worker bees, in contrast, have to make umpteen nectar-collecting trips to feed the hatching young back in the colony.
We were told there are 278 native species of bees. Most of these, 250, are solitary bees. These are the ones we gardeners can encourage with bee hotels, those little boxes of hollow canes, in which the bees can nest. There are 24 species of bumblebee, which all live in colonies. There are seven common ones in England. These are the ones I wanted to learn about, as they buzz around my garden and I knew nothing about them.
In the beginning is the queen
Their life cycle starts when a queen bumblebee wakes up after hibernation in the spring. She has been sleeping for nine months in a small hole she dug in a north-facing bank (north facing so as not to be woken by the occasional warmer rays of sun in late winter). She has already mated the previous Autumn and, on emergence, she slowly releases the stored sperm when she has eaten enough to redevelop her ovaries. She will feed herself up in order to be able to lay eggs to found a colony. So she spends about six weeks buzzing from flower to flower and zig-zagging around possible sites to set up her colony, usually found in a south-facing crevice of a building or tree. She will found a nest in an abandoned rodent hole, group her pollen together and lay eggs on top of it. She will also build a little waxy pot for nectar nearby. Once she has laid some eggs she has to provision it, with more pollen. No wonder the bumblebee is always busy!
The first eggs hatch out as worker bees. After a period as grubs, they turn into smaller versions of their queen, but without fully developed ovaries, and serve her devotedly in the communal tasks of cleaning the colony and foraging for food for the next generation of eggs. A worker bee with a full stomach of honey can stay in flight for 40 minutes of foraging. Once these worker bees get active, the queen has no need to leave the colony and she just stays there laying the rest of her eggs. Most bumblebees go through two colony cycles in a year. The colony looks like an untidy heap of wax, grubs and pollen. There may be mites crawling around too, but they are good for the bees as they help to clear the detritus. Towards the end of their season, the queen stops laying more worker bees, and produces male bumblebees and new queens.
Leaving home to find a mate
These males disperse away from their maternal nest and look for a queen from a different colony to mate with. There are seven of them for every queen, but most of them will die off within two weeks having failed to mate. The old queen with her worker bees dies in the autumn. Only the new generation of queens will go into hibernation in order to make a new colony the next spring. Even so, only about 50% survive the winter and, of those that do emerge, 50% die of disease or parasites such as nematodes. Continuous rain is also not good for bees.
There are other species dubbed cuckoo bumblebees that have a different life strategy. The fertilised female simply lays her eggs in the colony of the bumblebee she simulates. They then get hatched by the efforts of the worker bees there. A cuckoo bumblebee can be distinguished by the lack of corbicula (pollen basket) on its hind leg. These are the little sacks in which the pollen is carried back to a colony. Cuckoo bees buzz around each, feeding only themselves, as their eggs are fed by the worker bees of the colony they hide in. Cuckoo bumble bees have darker wings, a shinier body and fewer hairs on the legs.
Fur coats for warmth
The furry coats of bumble bees are signs of evolution in a coldish climate. They evolved about 34 million years ago in the Tibetan mountains. They cannot forage when temperatures are above 30ºC heat, but can in temperatures as low as 5c. They have an instinctive mechanism for keeping warm by shivering, which you can sometimes spot in a bee you observe in the early spring. With climate change, some species are moving northwards. In the Mediterranean they are active only in spring and autumn, not in the heat of summer.
I do not recall any in South Africa but one species, the carpenter bee, is prevalent, which bores holes in wood for its nest. Bumblebees have been introduced to the Southern hemisphere, in New Zealand for pollinating the clover crop, and across the Americas. However, in the Americas, honeybees from Europe introduced diseases which killed the native bumblebees and many native bumblebee species have declined as a result. Honey bees can compete with bumblebees for forage (the nectar and pollen), in that an increase in honey bees can affect the forage availability to other bees because they are seeking the same resource – nectar – in the same landscape.
Importance of diversity and renewed habitat
All bees (even those cuckoo bees) are valuable as pollinators. Honeybees and Bumblebees are generalists, liking different types of flowers, but many of the solitary bees are specific to only one or two flowers. Some have evolved long tongues, for instance, to get at the pollen/nectar in funnel-shaped flowers. Where bees are declining, it is because of intensive farming, pesticides, and the loss of wildflowers. If the population becomes isolated, there is not enough diversity for the males to find females from a different colony.
So it is very important to increase the habitat in which they can thrive, a vital task for the Bumblebee Conservation Trust which has specialist staff across the UK. Across their Bee Connected project, which works in South Kent and East Sussex, there are about 90 volunteers who assist with monthly walks recording their bee observations. This data enables the Bumblebee Conservation Trust to monitor how bumblebee populations are changing in time and zones, and to detect early signs of decline. But you first need to learn how to identify which bee!
I am pleased to say that I went into the workshop knowing only that most of the bumblebees I could see on lavender had buff behinds and two yellow stripes. Now I am equipped with colour identification pages, some knowledge of bee anatomy and habitat, and a desire to spot some more in the field. Hurrah – today I noticed a red-tailed one on the African marigold.