Introduction.
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There has been comment and discussion on social media recently around unmanaged colonies of honey bees living in the wild in the UK. Are they really wild, or are they swarms from managed colonies? Well, nobody knows because we don’t have details of their genetic histories. However, research in Ireland by Professor McCormack and colleagues shows that the free-living colonies studied recently are 99% pure Apis mellifera mellifera. Ireland has a history of managing locally adapted native bees and importing bees is much less common there than it is in the UK.
Does it matter what the genetics are when it comes to colonies that are managing to live in the wild by themselves? What might be more important is to look at is how honey bees live in the wild compared with managed colonies in apiaries. This is because the environment plays as much of an important role as genetics. Free-living colonies live in much smaller nest cavities, and they swarm more frequently than colonies prevented from swarming by control methods. Swarming allows brood breaks that help to control Varroa. However, taking swarms from those free-living colonies and leaving them unmanaged in an apiary is not the instant remedy for solving the Varroa problem. If these colonies are placed in large hives next to colonies with little resistance to Varroa and requiring treatments, they are unlikely to thrive unless they too are monitored for Varroa and treated accordingly. If, on the other hand, the beekeeper has been working carefully towards treatment-free beekeeping, as demonstrated by Westerham beekeepers, then the outcome is more likely to be favourable for a colony from the wild. https://westerham.kbka.org.uk/natural-beekeeping/
But let’s hear more on free-living colonies from an scientific expert today. I am very grateful to Professor Tom Seeley, our regular guest blogger, for his insightful account of locally adapted honey bees and free-living colonies, and why we should appreciate them. Thank you, Tom, for supplying this week’s Beelistener blog.
Valuing Free-Living Honey Bees.
Should a beekeeper value and protect the free-living colonies that have made their homes in trees and buildings near where he or she has an apiary? Or should a beekeeper aim to eliminate these free-living colonies, out of concern that they are sources of disease? As I see it, there are two good reasons for a beekeeper to desire the presence of free-living colonies.
The Value of Locally Adapted Bees.
The first reason is to sustain a population of locally-adapted colonies. Unlike managed colonies, which often have queens that were reared and became mated in places far away, and then were shipped to beekeepers, many free-living colonies have queens that were reared from local stock and became mated in their home region. This means that free-living colonies are far more likely than managed colonies to be well adapted to their environment.
A clear illustration of the value of having colonies that are locally adapted comes from an experiment that was conducted in France in the 1950s and 1960s. The essence of this experiment was the reciprocal exchange of colonies of Apis mellifera mellifera that were native to two distinct regions: Paris, in northern France; and Landes, in western France. It was known that the colonies native to these two regions have their peaks of brood rearing at different times of year: late Spring/early Summer for the Paris-based bees, and late Summer for the Landes-based bees. It was known, too, that in the region of Paris the major honey flows occur in late Spring and early Summer, whereas in the region of Landes there is just one strong honey flow, that from heather, Calluna vulgaris. (Fig. 1) It blooms in late Summer and early Autumn.
This colony-transplant study found something remarkable: the colonies from the two regions maintained their original annual rhythms of brood rearing in their new locations. This put their bouts of intense brood rearing out of synchrony with the principal honey flows in their new settings. The Landes-based colonies in Paris did not expand fast enough in Spring to thrive there, and the Paris-based colonies in Landes shrank too fast in Summer to produce good crops of heather honey. (Note: this makes me wonder if the colonies of Apis mellifera mellifera that are native to Scotland also have their peak of brood rearing in Summer rather than in Spring).
Disease Resistance.
The second reason for beekeepers to value the free-living colonies of honey bees that live nearby is to foster disease-resistant colonies. Unlike managed colonies, which often receive treatments for diseases, free-living colonies never receive these treatments. This means that free-living colonies experience strong natural selection for resistance to pathogens and parasites. Consequently, the workers in free-living colonies are more likely than those in managed colonies to possess physiological processes, behaviors, and other traits that give them resistance to pathogens and parasites. When the free-living colonies that have good disease-resistance skills produce drones and cast swarms, they enhance the local gene pool with the genes that underlie their means of resistance to pathogens and parasites.
An indication that this actually happens comes from studies of the behaviors that underlie the resistance of honey bees to Varroa mites and to the disease agents (e.g., the deformed-wing viruses) that are spread by these mites. Multiple groups of investigators—in the UK, Sweden, Norway, and France—have studied Varroa-resistant colonies, that is, colonies that survive without being treated for Varroa. One of their key findings is that the workers in the Varroa-resistant colonies are sensing which capped brood cells are infested with Varroa mites, and then these workers are uncapping, inspecting, and then recapping (without removing the pupae they hold) the infested brood cells. (Fig. 2) Evidently, the uncapping and recapping of these cells disrupts the reproduction of the Varroa mites in them, but it does not harm the pupal-stage worker bees that are inside these cells.
Conclusion.
So, it seems to me that free-living colonies of honey bees can be highly beneficial to beekeepers. They can help us to have locally adapted and Varroa-resistant colonies in our hives. I recommend, therefore, that we value and protect the free-living colonies we discover living in trees and buildings in the regions where we keep our bees.
References
Le Conte, Y. et al. (2007) Honey bee colonies that have survived Varroa destructor. Apidologie 3: 566-572.
Locke, B., and I. Fries (2011) Characteristics of honey bee colonies (Apis mellifera) in Sweden surviving Varroa destructor infestation. Apidologie 42:533-542.
Louveaux, J (1973) The acclimitization of bees to a heather region. Bee World 54: 105-111.
Oddie M.A.Y. et al. (2018) Rapid parallel evolution overcomes global honey bee parasite. Scientific Reports 8: 7044.
Oddie M.A.Y. et al. (2021) Reproductive success of the parasitic mite (Varroa destructor) is lower in honey bee colonies that target infested cells with recapping. Scientific Reports 11: 9133.
Hi Ann,
I can’t imagine that any beekeeper would want to exterminate ‘free living’ honey bees, but maybe I’m wrong. The degree to which they exchange genetics with nearby ‘kept’ honey bees probably varies with hive density. They will also exchange varroa mites and diseases with ‘kept’ bees in colony-dense locations.
I don’t think the fact that the tree-bees are alive necessarily means that they are highly resistant to varroa mites at the colony level. I expect that varroa mites are in such colonies, but regular swarming plus other behaviours mean that the population survives, even as multiple individual colonies do not. If both swarms and parent colonies in trees had low losses their population would explode, and I don’t think that’s what we observe. So they have high swarming and high losses, but the population survives.
The fact that honey bees live in trees (and other places) as well as man-made hives is a wonderful thing. However, the honey bees that beekeepers want; the sort that are gentle, low swarming, and highly productive, are the result of selective breeding by humans. I think both types can, and should, continue to co-exist.
Steve D
Hi Steve. Thank you for sharing your thoughts about how a population of free-living colonies persists. I have learned from monitoring the population of free-living colonies in the forests around Ithaca, New York, USA that each colony that is alive at the end of a winter (= an “established colony”) produces on average one swarm over the ensuing summer. Each swarm creates what I call a “founder colony”. So, at the end of a summer, the density of the free-living colonies is twice as high in these forests as it was at the end of the previous winter. However, because 20% of the established colonies perish over the next winter, and 80% of the founder colonies perish over this winter, the number of colonies in these forests is quite stable. If you would like a copy of the paper in which I report these studies, send me a letter via email to tds5@cornell.edu. –Tom S.
Thank you Ann for your wonderful insight and to Tom for his knowledge and research on free living colonies. The wisdom of the bees to manage and thrive in their wild colonies seems a good thing for beekeepers to have around them. Perhaps we can learn from the research that wild honey bees can certainly show us how it is done and welcome them.
It turns out that in populations of colonies that are not treated for Varroa (such as free-living colonies), one often finds colonies that possess methods of hampering the reproduction of Varroa. In my piece, I mention just one such method (perhaps the most powerful one): the uncapping and recapping of Varroa-infested brood cells. The second photo shows the sign of this uncapping/recapping response. It disrupts the lives of the mites in the capped brood cell. Another method of mite control by the worker bees is to bite off the legs of adult mites.
Thank you Ann and Tom for the support for locally adapted free-living honey bees. The biggest area of varroa resistant bees in the UK (and possibly Europe) exists in north-west Wales have likely benefited from free-living bees in the trees and old cavities in the region, that had been through the sieve of natural selection. Indeed, there are a couple of commercial bee businesses built out from capturing swarms from long standing free-living colonies in England.
The traits of naturally varroa resistant bees are now well known (not frequent swarming!) and with education, will become more widely understood in the beekeeper community. They are easy to observe and accessible to all
Thank you, Steve, for the information about north-west Wales as a large area in the UK with varroa-resistant colonies. I wonder why this is. Is there low a relatively density of beekeepers (but plenty of free-living colonies)? Or are there plenty of beekeepers but they tend to avoid importing queens and rely instead on rearing their own queens from survivor colonies, capturing swarms, and doing cut outs? Thanks, too, for you and your club’s work to produce and promote queens for Varroa-resistant colonies.
Your question Tom also has the answers! They have a voluntary conservation area for the dark Welsh bee (Amm) and imported stock is frowned upon. Using local bees, benefiting from unmanaged colonies in the area, their traits, including varroa resistance, have embedded locally and stabilised over the years. There are about 500 managed colonies across a large area. It is a fine example of what is possible.
Thank you, Steve, for explaining how the beekeepers in northwest Wales have a conservation area in which it is frowned upon to import bees and there is a substantial population of free-living colonies. I think we can take real hope from this example, and from the example of the free-living colonies thriving in the vast forests of the northeastern U.S.
I suspect you know, too, that honey bees have some special genetic tricks–super high rates of genetic recombination when queens produce their eggs, and extremely high polyandry—that help ensure that there is a great deal of genetic variation among the colonies in area. This variation is the “fuel” for the evolution of disease resistance by natural selection.
I have built up my bees now over the past 8 or more years using caught feral/wild swarms and through careful selection I now have bees tolerant of varroa and of good quality in all of the required traits. They are all caught bees but are not swarmy so I can assume that swarming is not a main reason for their surviving without treatments but they do have brood breaks in mid summer when they fill the brood nest with nectar which stops the queen from laying and of course in the winter also.
In the wild these bees could well swarm annually if not managed but according to Tom Seeley only about one fifth survive their first winter and of course there is also a limit on how many bees can survive in a certain area depending on forage availability etc. which would explain the fact that they are not increasing over a certain density.
In hindsight, all of our honey bees have been bred over the years from wild bees by careful selection so it would be no harm for people to start to breed bees from swarms, either in a mixed apiary or a selected one for the purpose to attempt to raise bees capable of coping with varroa. I would have no problem with putting fresh swarms in my apiaries because I know they will not spread disease to my other bees. My established hives have virtually no varroa to spread around and likewise swarms that I have caught lately are virtually varroa free. I couldn’t vouch for any that come from managed bees but luckily there are few beekeepers in the area who are going to lose more than a very occasional swarm.
Thank you, Alan, for sharing your success in capturing swarms from free-living colonies and thereby having colonies that survive without chemical treatments for Varroa.
Thanks, too, for providing some insights about why, even though free-living colonies produce swarms, there is not a population explosion of these colonies. Regarding the population of free-living colonies that I study (in the vast forests around Ithaca, in New York State), I have found that about 20% of the established free-living colonies die out over winter, and that about 80% the founder free-living colonies (i.e., the colonies started by swarms in a given summer) die out over their first winter. So it works out that the 20% of the new colonies that survive over a winter replace the 20% of the established colonies that perish over a winter. Hence there is not an “explosion” in the number of free-living colonies where I live.
And by the way, my colleagues and I have done a sophisticated genetic comparison of worker bees collected from the wild colonies 20 years before and 20 years after the arrival of Varroa here. It shows that the wild colonies experienced a major die back (they went through a genetic bottleneck) but have come through this OK. Will send you a pdf of the paper if you’d like to study it.
Many thanks for your concise explanation about the stable number of colonies in certain areas. Much of my knowledge about treatment free bees came from your publications (I am still waiting for the new book with anticipation). I would love to read the papers you mention so I will email you shortly using a previous e mail that you sent to me. Thanks again
Great discussion here about varroa and bees without treatment.
With your approval, I will add more situations that affects the development of varroa:
1. cell size, which is smaller in nature
2. a beehive provides less insulation than a tree
3. every intervention affects the environment in the hive and opens the cracks between the boxes, compared to no intervention in nature
4. we have high density of hives in one location compared to low density in nature
5. the arrangement of the frames is straight in the hive, but random in nature.
Hello Florin,
Thank you for contributing to the discussion. Have you read the Seeley and Griffiths paper that reports on discovering that small cell size comb has no negative impact on Varroa development? DOI: 10.1007/s13592-011-0054-4
If you cannot access the paper send me an email.
Best wishes,
Ann.
Yes, I have read the Seeley and Griffiths paper about small cell comb, but with all due respect to the researchers, I think it is done for a too short period of time to be considered above other research that says otherwise.
In my opinion, long-term bee research is the most accurate.
All the best.
Florin.
Interesting, Florin. The long-term research you mention is worth reviewing.Please can you share links to it with us?
Many thanks, Ann.
It is true that our study ran for only four months (mid-June to mid-October). This is approximately 6 brood cycles. But it is also true that in all our measurements of the mite levels in the colonies that we made across these 4 months, we NEVER found a difference in the mite levels (no. of mites per 100 bees) between the 7 control colonies (cells 5.38 mm wall-to-wall) and the 7 treatment colonies (cells 4.90 mm wall-to-wall). I feel it is reasonable to conclude that, at least in our study, we found no evidence that small-cell combs helped colonies control the level of Varroa mites. Our findings match those of parallel studies conducted in Ireland by Coffey et al. (2010) and in the U.S. by Ellis et al. (2009) and Berry et al. (2010).
I wish that small-cell combs were an effective, non-chemical way for beekeepers to control Varroa, but I conclude that all the careful experimental studies done in Europe and North America on this idea have found no evidence that using small-cell combs is an effective method of Varroa mite control.
In my opinion, the cell size discussions are wrong because a standard size (5.40mm) is considered a normal size and a natural size is considered a small size, which is absurd.
That’s why I think it’s right to do the research for the standard size in relation to the normal size and not the other way around.
Regarding of your research on small cell size, I believe that the time period (late summer and fall) may affect the results because the bee population is decreasing and the mite population is increasing.
In the spring, the research could have a positive effect for small cells, taking into account that a colony with small cells could raise slightly more bees.
Another situation is that most of the beekeepers only read the title and abstract of a research and in most cases they will only remember the title.
In your title research there is a negation between small cell comb and varroa control mites that is perceived by beekeepers that the standard size is better for varroa control than the small size, which is incorrect. I can’t explain it very well, but it’s something psychological.
With all due respect for your work, but this is my honest opinion.
All the best.
Florin.