Bumblebees are among the most endearing and familiar of our insects. The sight and sound of bees droning methodically from flower to flower is a quintessential part of a summer’s day. Sadly, changes to the farmed countryside have not been kind to our bumblebees. The number of species found in most of lowland Britain has halved since 1950. Three species have gone nationally extinct and several more may follow in the near future unless we act quickly. The reason that bumblebees have declined in the countryside is simple. Bees feed exclusively on pollen and nectar, and there are far fewer flowers in the countryside than there once were. Hedges have been grubbed up and marshes drained. In particular, unimproved grasslands which are rich in wildflowers (haymeadows and chalk downland) have been almost entirely swept away, replaced by silage and cereal fields.

Right, a Tree Bumblebee (Bombus hypnorum) feeding on bistort

Gardens now provide a valuable flower-rich refuge in an impoverished landscape, and as a result have become a stronghold for some bumblebee species. Depending on where you live, and what flowers you grow, you may see up to a dozen bumblebee species in your garden. Even a casual inspection of flowers in a garden or park will reveal several very differently coloured bumblebees. In fact six or seven species can be found in almost any reasonable-sized garden, and if the right sorts of plants are grown this total can be doubled.

Left, several different species enjoying cardoon (S. Jenkins)

The Bumblebee Lifecycle

Bumblebees, honeybees, wasps and ants are all social insects: they live in a colony with a queen and her daughters (the workers). Bumblebees have an annual lifecycle, with new nests being started each spring by queens. The queen bumblebees are very large, and from February onwards can be seen feeding on flowers such as willow catkins, bluebells and lungwort, or flying low over the ground searching for a nest site. Some species prefer to nest underground in abandoned burrows of rodents, while others nest just above the ground in dense grass or leaf-litter. The queen stocks her nest with pollen and nectar, and lays her first batch of eggs. She incubates them much as a bird would, sitting on the eggs while shivering her flight muscles to produce warmth. When the eggs hatch the legless grubs consume pollen and nectar, grow rapidly, and pupate after a few weeks. A few days later the first workers hatch from their pupae and begin helping their mother, expanding the nest and gathering food. By mid-summer nests of some species can contain several hundred workers. At this point the queen starts laying both male and female eggs. The females are fed extra food and become future queens. Both males and new queens leave the nest to mate, and the new queens burrow into the ground to wait until the following spring. The males, workers, and the old queen die off in the autumn, leaving the nest to decay.

Right, inside a bumblebee's nest

Cuckoo Bumblebees

In the UK there are 6 species of cuckoo bumblebees. These were once themselves like other bumblebees, but they have switched to a parasitic existence. The females are especially powerful, and force their way into the nests of their bumblebee hosts. They kill or evict the queen and take over her workers as their own, using them to rear their own offspring. Cuckoo bumblebees do not produce workers of their own. Each cuckoo species tends to attack a particular species of bumblebee, so for example the southern cuckoo bumblebee targets buff-tailed bumblebee nests.

There are so many fascinating facts about bumblebees - far to much to fit on the website. Did you know that bumblebees have smelly feet? Are bumblebees left-handed or right-handed? Why do inbred bumblebees turn male? Why do workers turn on their mother and murder her? Where do bumblebees mate? How far can a bumblebee fly?

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