Hopefully many of you have noticed the increasing numbers of bumblebees and other insects outside and in your gardens over the last few months. You may have asked yourself, where did these bees go during the winter? Where have they all come from now? The answer lies in the story of the devoted bumblebee queen…
A long sleep
By the end of the Summer season, almost all of a bumblebee colony perishes – that is, all except the young virgin queens called gynes. After leaving the colony in which she was born, a gyne is mated with by a male from a different colony. Instinctively, she seeks out a quiet, dark place (such as in loose soil) in which she can safely ‘hibernate’ during the cold, long Winter months. 1 During this long, food-deprived period (called diapause), she relies on her crucial fat-reserves to survive. 1 This can be as long as 6 to 9 months without food! 2
Evidence has also been found to suggest that hibernating gynes have high levels of proteins that store amino acids. 3 This may help to maintain normal biological functioning of the vulnerable gyne throughout her extended sleep.
Spring, finally!
It’s a tough world for a bumblebee Queen emerging from her long, Winter hibernation. She has been ‘asleep’ for many, many months. Not only has she not eaten during this time, she now is faced with a series of daunting challenges that stand in her way of producing a successful colony of her own.
During her hibernation, she can gather quite a number of mites on her body, which are essentially hitchhikers that hope to catch a ride to the queen’s new nest once she wakes up. These mites often just feed on pollen, sometimes nectar, but sometimes the loads can become so heavy that they can easily hinder a bee’s ability to even fly. 1,4,5
And a queen really needs to fly. Bumblebee queens must visit up to 6000 flowers per day to get the energy they need to be able to fly, look for a nest and eventually incubate their first batch of precious eggs. 6 This is quite the task in early Spring, when floral resources are limited. 6
What nest is best?
House-hunting is a difficult task for a Queen looking to rear up to hundreds of future offspring. And different species have different preferences. Many bumblebee species, such as the buff-tailed bumblebee (B. terrestris) pictured above, like to nest in the privacy of underground. The buff-tailed and the white-tailed (B. lucorum) bumblebees particularly like to use empty rodent nests. Others, such as the tree bumblebee (B. hypnorum) prefer to nest over ground or in trees. 1,7
To my delight, I recently found an Early-Bumblebee (B. pratorum, an opportunistic species 1) nest in my garden under a compost heap.
(©Kim Taylor) Image source: Naturepl
Making a house a home
Once she finds an appropriate property, the queen bumblebee starts making her nest lovely and cosy through building a hollowed-out, lined, tennis-ball sized mound using materials she finds nearby. 1,7 The Amazonian bumblebee (B. transversalis) even makes a waterproof roof for her nest. 8 Using her powerful wing muscles, she heats her body up (sometimes even reaching 38°C) and eliminates any moisture or dampness in the nest. 7 After a few foraging trips, she uses the nectar she’s collected to insulate the walls and floor of her new home. 7
Establishing her colony
Her ovaries have now developed, and wax starts secreting from her abdomen. She collects pollen using specialised ‘pollen-baskets’ on her legs and moulds it into pyramid-like lump. 1 It is on this lump she lays her very first batch of eggs. Bumblebee eggs are sausage shaped, pearly white in colour. 7
Over the coming weeks, these eggs will grow under the careful watch of their mother, who provisions them with food and long, dedicated periods of incubation. 1,7Incubation is tiring work, so the Queen cleverly constructs a nectar pot beside the egg clump so she never has to go too far for an energy drink. 7
These will eventually emerge as miniature versions of herself: the worker bees. All worker bees are female, who then help their mother by collecting food as she continues to lay eggs and incubate brood, leading the colony to grow and grow. 7
Eventually, towards the end of the season, the colony starts producing males and, of course, the large gynes. These gynes will follow in the footsteps of their mother’s journey, from hibernation to founding a nest of their own, and will carry on the legacy of the colony even after all the others, including their devoted, exhausted mother, are all long gone.
What you can do to help…
Visit http://pollinators.ie/ to find out what you can do to help bumblebee Queens, their colonies and other important pollinators survive challenging times of the year.
References
- Goulson, D. (2003). Bumblebees: their behaviour and ecology. Oxford University Press, USA.
- Alford, D. V. (1969). A study of the hibernation of bumblebees (Hymenoptera: Bombidae) in southern England. The Journal of Animal Ecology, 149-170.
- Colgan, T. J., Carolan, J. C., Bridgett, S. J., Sumner, S., Blaxter, M. L., & Brown, M. J. (2011). Polyphenism in social insects: insights from a transcriptome-wide analysis of gene expression in the life stages of the key pollinator, Bombus terrestris. BMC genomics, 12(1), 623.
- Houck, M. A. (2012). Mites: ecological and evolutionary analyses of life-history patterns. Springer Science & Business Media.
- Schwarz, H. H., Huck, K., & Schmid-Hempel, P. (1996). Prevalence and host preferences of mesostigmatic mites (Acari: Anactinochaeta) phoretic on Swiss bumble bees (Hymenoptera: Apidae). Journal of the Kansas Entomological Society, 35-42.
- National Biodiversity Data Centre. Summary notes on Ireland’s bees. National Biodiversity Data Centre. [Accessed 18.05.19 at http://www.biodiversityireland.ie/wordpress/wp-content/uploads/Summary-note-on-Irelands-bees.pdf]
- Alford, D. V. (1978). The life of the bumblebee. Davis-Poynter.Taylor, O. M., & Cameron, S. A. (2003). Nest construction and architecture of the Amazonian bumble bee (Hymenoptera: Apidae). Apidologie, 34(4), 321-331.
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