Flight season: March into September.
Flowers visited: Blackthorn, dandelions and cherry in spring; thistle and brambles as well as a wide variety of garden plants such as lavender in the later season.
Nesting preferences: The parasite of the buff-tailed bumblebee, Bombus terrestris.
Status: The commonest cuckoo bee in much of the UK.
Similar species: Similar to the rarer bohemian cuckoo bee, Bombus bohemicus, but tends to be ‘blacker’ and a bit larger.
Description: The vestal cuckoo bee, Bombus vestalis is a parasite of the buff-tailed Bumblebee. To ensure the survival of her brood she has to have some morphological adaptations and differences to the social bumblebees. She is large and has a thicker cuticle to allow more muscle attachments to her limbs. Flying with a deeper hum than her social cousins, she identifies a nest of the buff-tailed bumble. Darting inside, she hides at the bottom of the nest, well away from the buzz of the colony. She hides because the hydrocarbons on her body are different to that of the colony’s and so she is easily detectable as an intruder. A few days in the colony will ensure that she begins to smell like the other bees. She now launches her attack. The bigger, stronger cuckoo bee overpowers the original queen, either killing her or, more rarely, forcing her into subservience. Now in charge, the cuckoo will lay her eggs and the enslaved workers will tend to them for her. All the eggs are fertile and will leave as they hatch. This means the colony will not survive much longer as workers are not replaced. However, the cuckoo bee will have passed on her genes to the next generation and so her cycle will successfully continue.
Where to see them: Overall, probably the commonest cuckoo bee in the valley and certainly the one that you are most likely to see in your garden. I have found no real pattern in their distribution other than quite abundant everywhere, probably because their host (B. terrestris) is very abundant.