Garden bumblebee (Bombus hortorum)
One of the ‘Big 7’ widespread and abundant species, found in a wide range of habitats across the UK and often frequent in gardens, where it is one of two common species found visiting foxglove. All three castes are similar, with a yellow-black-yellow thorax, a yellow band at the base of the abdomen, and a pure white tail.
The species is parasitized by the similar-looking Barbut’s cuckoo-bumblebee (Bombus barbutellus), but the cuckoo does not have pollen baskets. Both it and the Heath bumblebee (Bombus jonellus) also have round faces only as long as they are wide, whereas the Garden bumblebee has a face between 1.1 and 1.4 times as long as wide. The male genital capsule is useful to check the ID, particularly of worn specimens.
The Ruderal bumblebee (Bombus ruderatus), sometimes known as the Large garden bumblebee, is very similar to the Garden bumblebee, and some individuals may prove impossible to differentiate, particularly in the field. Males of the Garden bumblebee (Bombus hortorum) have black hair around the mandibles where the Ruderal bumblebee have ginger, but females are more difficult to separate, and the only fully reliable method is to measure the length of the face: the Ruderal bumblebee has a longer face than the Garden bumblebee, more than 1.5 times as long as wide. Generally, the thoracic yellow bands are more equal in the Ruderal bumblebee (the Garden bumblebee has a wider front band than back), and the abdominal band in the Garden bumblebee often extends backwards onto the second abdominal segment. The Garden bumblebee is also generally less neat in appearance than the Ruderal bumblebee, which has very even-length hair. The Ruderal bumblebee produces melanic (all black) individuals far more frequently than the Garden bumblebee, or indeed any other British bumblebee species, and all-black bumblebees are likely to be that species.
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For more detailed information visit: http://www.bwars.com/index.php?q=bee/apidae/bombus-hortorum