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Rasbak

Tree bumblebees (Bombus hypnorum) in a bird box © Rasbak

Tree bumblebee

Rasbak

Fast facts

  • Latin name: Bombus hypnorum
  • Notable feature: Black bumblebee with white tail and ginger thorax
  • Rarity in UK: Rare / Common
  • Where in the UK: England, Scotland and Wales
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At this time of year, we regularly get calls from concerned members of the public about swarms of bees around houses which look too big and furry to be honeybees. 

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This unusual behaviour usually turns out to be our newest bumblebee arrival, the Tree bumblebee (Bombus hypnorum).

The Tree bumblebee only arrived in the UK in 2001 and then rapidly spreading north, with it being recorded for the first time in Scotland in 2013. This bumblebee does really well in the UK. It is a generalist species which means it feeds on a wide range of flowers though it is particularly fond of raspberries and blackberries, making gardens and allotments great places to see them.

High life

This adaptable bee is the most arboreal of all bumblebees and will nest in abandoned bird boxes or empty roof cavities. However some can be found nesting low down in old mouse nests or even in the fluff of tumble drier vent pipes. One Buglife member of staff found a nest in her lawn - clearly no one had told this particular colony that they were supposed to be Tree bumblebees!

Surveillance

Tree bumblebees aren’t particularly aggressive, although they are likely to defend their nest if they feel threatened. We get a number of calls during the months of May and June because of unusual nest activity – clouds of bees ‘swarming’ at the entrance to the nest. This behaviour can last all throughout the day, and may involve a number of bees.

But don’t panic! This is actually something called ‘Nest surveillance’ and it’s the frisky males hanging around. Male bumblebees cannot sting as they don’t have a stinger (the stingers are modified egg laying tubes called ovipositors which obviously only females will have).

The males are just waiting for the virgin queens to emerge and once they do, the males will attempt to mate with them, very often falling to ground during the process. Once the queens have mated they feed themselves up and find a hibernation spot, ready to start a new colony next year. These fantastic pollinators don’t appear to be harming our native wildlife and they are truly wonderful to watch in flight.

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