Branching out: A new (Tree) Bumblebee for Devon

Some may be aware of a recent addition to our list of 25 indigenous bumblebee species. Six of these are common:  Bombus terrestris - the Buff-tailed Bee; Bombus lucorum - the White tailed Bee; Bombus hortorum - the Garden Bee; Bombus pratorum - the Early Bee; Bombus lapidarius – the Red tailed Bee; and Bombus pascuorum - the Common Carder Bumblebee. Now there is a new continental species in our midst.

Since it was first recorded, at Langford, Wiltshire, in 2001, the Tree Bumblebee Bombus hypnorum, has been spreading in Britain.  One of the earliest of the few records from  East Devon was in August 2010, in the Exmouth area. 2011 however, has seen a marked increase in the number of Devon sightings.

The Tree Bumblebee is of medium size, with a black face as long as wide, a ginger haired thorax, black abdomen and white tail. Only the male has some ginger on the thoracic end of its abdomen and a rusty/yellow face.They appear to be fairly cosmopolitan in their habitat and nectar preferences.

This year I have recorded this species in many places, including my garden and meadow near Harpford, Exeter Sludge Beds Reserve by the Exeter Canal; Tiverton Canal; near the Borrow Pit entrance at Seaton Marshes; Ashclyst Forest and Exmouth coastal path.

The Tree Bumblebee is an early brood species. Fertilized queens emerge from winter hibernation in February/early March. They hunt for a suitable above ground nesting site. These can include rotten holes in trees (hence its name); a bird box or a disused mammal hole. The nest is at its most productive late May-early July. Partial second broods have been recorded.

This bee has now spread throughout England- Northumbria, and the Home Counties to Cornwall and into Wales (the Gower) and is still spreading. After ten years the species has almost reached the Scottish border! All this provides an excellent opportunity to analyse their behaviour and breeding patterns. This research is being currently undertaken by BWARS (Bees,Wasps and Ants Recording Society)-

We all can help to follow the spread of the Tree Bumblebee by recording any sightings of it. (i.e., who, what, where and when!) Send all records to the Devon Records Centre, or to Mike Edwards at BWARS. The colonization of Britain by Bombus hypnorum can also be followed on their website (www.bwars.com), where there are also excellent colour photographs.
 
Incidentally. the White Tailed Bumblebee Bombus lucorum agg may be an aggregate made up of up to eight different species! If this is indeed so, it will increase our number of indigenous Bumblebee species but will also certainly complicate bumblebee identification in the field. Identification of bumblebees is not as easy as is often assumed and it is important to check, particularly if the bee you have seen apears to be something unusual. Luckily, the Tree Bumblebee is one of the ‘easier’ bumblebees to record.