An Introduction to Bumblebees

Did you know there are over 20,000 species of bee in the world?

From the solitary leafcutter bee which lines its nest with cut leaves to the famous honeybee which lives in a colony with up to 80,000 sisters, each and every species has a part to play in our ecosystems. However, each and every species is also facing unique threats. Therefore, when it comes to conservation, I think it’s important to specify which bee we’re talking about when we say: ‘save the bees’.

As a bumblebee scientist, it seems fitting to begin with our fluffiest friends.

There are over 250 species of bumblebee worldwide, and the UK is home to 24 of them — not including two extinct species. Most bumblebee species are eusocial. This means that, like honeybees, they live in a colony made up of a queen, worker bees, and male bees. However, unlike honeybees, bumblebee colonies are small. A well-established colony is home to 400 bumblebee workers at most!

Queens of eusocial bumblebee species emerge from hibernation in early spring, looking for food and nesting sites. Once a nest has been founded - usually in the ground - the queen will lay her eggs and continue foraging for herself and her larvae. If she is successful, the larvae will grow into worker bees and take over foraging duties while the queen continues laying eggs. Towards the end of the summer, the queen will start producing males and virgin queens which will eventually leave the nest to mate with males and virgin queens from other colonies. The old queens, workers, and males die at the end of summer, while the new queens go into hibernation ready to start the cycle again the following spring.

A small number of bumblebee species are known as cuckoo bumblebees. Not quite solitary and not quite eusocial, they are cleptoparasitic. This means that, like the birds they are named after, they invade the nests of other bumblebee species for the purposes of reproduction. A cuckoo bumblebee female will kill or subdue the queen of a vulnerable bumblebee colony and take the nest for her own, using pheromones or physical attacks to force the workers into feeding her and raising her young.

The vast majority of bumblebee species are excellent pollinators. They are extremely efficient, capable of doing the work of thousands of honeybees with a fraction of the numbers. This is down to a number of reasons:

1. Unlike honeybees and wasps, their bodies are covered in hair. Pollen clings to the hair of a visiting bumblebee where it will be transported to another plant with no additional effort on the bumblebee’s behalf.
2. Depending on the species, bumblebees may have short tongues or long tongues, each adapted for foraging on different plants. This means that, as a group, they are able to pollinate a wider range of plants than a single honeybee species, for example.
3. Unlike honeybees, bumblebees can perform buzz pollination. By contracting their flight muscles, they can produce vibrations which release pollen from even the most conservative plants. Blueberries, potatoes, and tomatoes are just some of the plants which require buzz pollination.

Bumblebees are suffering widespread declines across the UK, and this is mainly due to loss of habitat. Bumblebees thrive in flower-rich environments, but sadly, the UK has lost over 98% of its wildflower meadows since the 1940s. Furthermore, agricultural intensification due to an ever-growing demand for food has led to increased use of harmful pesticides and herbicides, indiscriminate mechanised farming technologies, and a huge reduction in wild land area.

Due to bee-washing, many people are under the impression that it is honeybees which need our help. Although it is true that the vast majority of crop pollination is performed by honeybees, this is because they are domesticated by humans for pollination purposes. This means that they are cared for by beekeepers who treat disease, provide food when resources are low, and provide shelter from pests. Because of this, honeybee numbers are stable — unlike those of wild bees and other pollinators.

The decline of bumblebee numbers in particular has a measurable economic impact on global economies. However, bumblebee pollination also plays a vital role in complex food chains, and this is vastly more important. Without bumblebees, entire ecosystems would collapse and the consequences would be devastating.

Scientists like me are doing what we can to build a body of research which will go on to inform landowners and policymakers in their future conservation efforts. However, there are a number of things individuals can do (for example, wild gardening) to help bumblebees, too.

I’ll leave you with a question: how many bumblebee species can you name from memory?