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Meet the Tree Bumblebee!

The Tree Bumblebee (Bombus hypnorum) is a relative newcomer to the UK. Since its arrival from France in 2001, it has been rapidly expanding its range throughout England and Wales. So much so, it can now be grouped in with our most common bumblebee species – the ‘Big 7’. 

Easy to identify, this very distinct species has an all-ginger top half (thorax), a black middle (abdomen) and a distinctive white tail. The male, worker and queen bumblebees all look the same, only differing in size. In addition, when the males are first born they have some ginger facial hair which they often lose over time. Workers are regularly seen with a shiny round black spot on their thorax – this is a bald spot caused by the general wear and tear of foraging in flowers and rubbing up against materials in the nest.

Tree Bumblebee (Bombus hypnorum)
Tree Bumblebee (Bombus hypnorum)

One reason they may seem so common is that they are a remarkably urban species, often choosing to nest in bird boxes (they have been known to evict blue tits!) or roof eaves, meaning that they frequently nest in close proximity to people’s houses and therefore are very noticeable. 

Each year at the Bumblebee Conservation Trust, we are inundated with enquiries about Tree bumblebee nests and behaviours – as have many honeybee keepers. One reason for this is that Tree bumblebees exhibit a unique mating behaviour in comparison to other bumblebees, where many males (drones) congregate in the air space around the nest entrance on a daily basis. This ‘swarm’ is called a drone cloud. They maintain surveillance-type flight paths waiting for a new queen to emerge. When a new queen does make an appearance, males fly right into her (you can often hear the collision!) and the two bees fall to the ground. The male attempts to mate with her and she attempts to shake him off – often the males receive a nasty sting (whether successful or not) and die. On a hot sunny day the amount of males outside a nest can get to well over 50. Many people find this intimidating but it is important to bear in mind male bees can’t sting and are only interested in one thing – mating! 

That said, Tree bumblebees can be a little more sensitive than our native bumbles to disturbance. If their nests are exposed to vibrations, workers will often erupt out of the nest in large numbers to investigate what the disturbance is and can potentially sting an intruder.

It is mainly because of these behaviours - urban nest location, drone clouds and defensiveness - that we receive calls from worried residents who have never experienced bumblebees at such close quarters before. We often find that people just need reassurance about the bumblebee lifecycle: nests only last for about two months, after which time new queens leave to hibernate in the soil and the remaining workers and males disband and die. Their nests don’t cause damage and as long as they are left undisturbed, the bees will live in harmony with people, meaning no harm should come to either party.

The more education we can offer people regarding bumblebees, the more comfortable people will feel living with their summer lodgers. One thing is for certain - Tree bumblebees are here to stay and we will have to learn to live alongside our new bumbles and even promote the hard work they do pollinating our crops.

Photo credits: Andrea Finch and Les Moore