September 2017 - Tree Bumblebees

There have been several reports of bumblebees in bird-boxes in Bawburgh this year. The bumblebee that does this most is the tree bumblebee (Bombus hypnorum), although they also nest in trees, and under roof tiles and house eaves etc.  This bee was first seen in the UK, in Wiltshire 2001, presumably arriving from Mainland Europe, where they are common; since then they have spread throughout England and Wales and in 2013 reached Scotland. By using bird-boxes, they have ready-made nest sites, undoubtedly helping their distribution success.

In appearance, this bumblebee looks like a punk rocker, with hairy reddish-brown thorax, black abdomen and white tail. The queen looks for a suitable site to set up a colony as early as March/April and will even evict tits already starting to nest, using the convenient pre-gathered nest material. Once the nest is set up, the queen will forage for nectar and pollen, for herself and her initial brood. Gradually over about 2 months the colony multiplies, initially consisting of forager bees and eventually also smaller home sitters.  Then large males (drones) appear (twice the size of a honeybee). Once these leave the nest they will never return. It is these drones that may cause public concern as they 'swarm' around the hive, an event that occurs between May and July. This activity is known as 'nest surveillance flights', and appears like an 'aerial dance' with the drones all pointing towards the nest's entrance.  This is a mating preparation characteristic of these bees. It may look a bit like a swarm but no more than about 20 drones are involved. This activity may last several weeks, only occurs in daylight hours, increasing during warm sunny weather; cold rainy weather reduces the activity. Drones move from nest to nest in their search, probably following a patrol route. During this time, normal nest activity continues regardless of the hovering drones. Occasionally drones dart towards each other and fall out of the air with an audible bang; this is erroneous mating activity. When eventually the virgin queens emerge from the nest to fly, the drones will attempt to mate giving the appearance of fighting. Paired bees fall to the ground, where they remain coupled for some time. The freshly mated queens will then build up body food reserves in preparation for hibernation. The following spring they will look for a nest site and the cycle repeats. The total colony only lasts a few months before it dies.

Although bumblebees produce honey there is no surplus to be harvested.

The passive bumblebee can sting multiple times if a threat to themselves or the nest is perceived. Vibrations are considered threats.

 

lingibson@bawburghvillage.co.uk

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