HYMENOPTERA > APOCRITA | Aculeata > APOIDEA > Apidae

Also known as the Vestal Cuckoo Bee, Bombus vestalis is a social parasite where freshly emerged females, that will already have mated, seek out newly established nests of their favoured host species which, in this case, is the common Buff-tailed Bumblebee, Bombus terrestris. Once a suitable nest has been found the female will either dominate, or more likely kill, the incumbent host queen so that she can take over the egg laying in the colony. Her offspring will only be new female or male Bombus vestalis, which will take no part in the colony as all the work will continue to be done by the host workers.

Females are large, about the same size as a queen Bombus terrestris. They have a deep black, short-piled velvety body with a ginger or buff coloured collar at the front of the thorax and a white tail with yellow side patches. These patches are a bright sulphur-yellow in fresh specimens, but tend to bleach out with age as does the collar, which by the end of the season will more than likely have faded to a pale straw colour. The females never have any hint of a midriff band.

The slightly smaller males have a not dissimilar appearance, although their collar band is more of a dark yellow colour and the white tail has a complete yellow ring at the base rather than side patches. In fresh specimens this band is a bright sulphur yellow colour. A weak midriff band may also be evident but, if present, it will be restricted to the first tergite. Another very noticeable feature of the males is that they have much longer antennae.

As with all cuckoo bumblebees the wing membranes are a tad darker than those found in the social species, the head is wider and more box-shaped, the body is generally less hairy which allows the shiny exoskeleton to show through, and the hind legs are hairy in both sexes as the females have no need for a pollen basket as there is no worker caste.  

Bombus vestalis is a relatively common and widely distributed species across central and southern England, but seemingly quite scarce in Wales and, although spreading northwards, far less frequent up country and into Scotland. They occur in a variety of habitats including woodland, meadows and gardens or anywhere really that their host species is present.

Faded individuals could be confused with their northern counterpart, the Gypsy Cuckoo Bumblebee, Bombus bohemicus, but that species has only been recoded once in Dorset (VC9) over forty years ago and only three times in South Hampshire (VC11) so it's not one I'm going to worry about. 

Females typically start emerging from hibernation at the end of March or early April, with the males following a couple of months later around the end of May. They can usually be seen right through the summer months up to the end of September. When the females first appear, they may be seen flying close to the ground in search of potential Bombus terrestris nests. They're a relatively short-tongued species so tend to favour plants such as sallow catkins, dandelions and knapweeds. Later in the year, males can be abundant on umbellifers, thistles and brambles.