[5] It is similar in appearance to another cuckoo bumblebee, Bombus bohemicus, but is distinguishable by either the length of the antennal segments or dissection and comparison of the genitalia.

[6] A key characteristic of Bombus vestalis is the lack of corbiculae or a pollen basket on the hind legs of the bee.

With its larger body and poor foraging skills, the female Bombus vestalis are adapted to taking over nests of other species which have already been made and using the workers in these colonies to collect pollen.

[8] This is evolutionarily beneficial since the female is the sex which takes over host species and allows Bombus vestalis to reproduce.

In fact, many of the male bees which are hatched in a nest that has been taken over by Bombus vestalis are a result of host workers who were able to successfully lay eggs despite the aggression of the invaders.

They have similar mandible and body structures, and it is likely that the differences are only derived from chromosomal alterations during development of the embryo.

[5] Using data from the National Biodiversity Network gateway, Bombus vestalis is most prominent in south-east England.

In the spring, the emerging queens frequently fly to flowers such as deadnettles, sallows, blackthorns, and dandelions.

[4] The life cycle of Bombus vestalis is dependent on its host B. terrestris, who begin the growth of their colony in the early spring, slowly building up the nest.

In taking over the nest, the invaders assert their dominance among the workers bees for the first few days without killing the queen.

[8] Male Bombus vestalis have been found to be attracted to floral odors, particularly the polar compounds of Ophrys flowers, which mimic the sex pheromones of virgin females.

In short, olfactory cues play an essential role to attract males, for virgin female Bombus vestalis, and their sexually deceptive orchid mimics, O. chestermanii and O. normanii.

[11] Since B. vestalis is so perceptive of these odors, she knows which worker bees to kill so that the brood of eggs is safely and solely her own.

The remaining younger Bombus terrestris and those born soon after takeover of the queen are available to help care for the new B. vestalis nest.

[11] With a smaller colony to take over, the female B. vestalis can individually kill off the workers in the B. terrestris nest.