Small cell foundation

In a recent monthly newsletter Thorne’s announced they were now supplying small cell foundation. This foundation has a cell diameter of 4.9mm, rather than the standard 5.2-5.4mm. Under the ambiguous heading 4.9 mm foundation for varroa control” they have the following text:

Wired foundation

Wired foundation

“It is claimed varroa mites struggle to reproduce in the slightly smaller cell size. 4.9 mm being close to what bees produce in comb width in nature. Many beekeepers in the USA who have experimented with small cell have reported encouraging results. Moving over to small cell however can be difficult and must be done at the correct time of year. It cannot be done either by simply putting 10 frames of small cell foundation in the hive. The bees must first be subject to regression over a period of several months.”

Do mites struggle to reproduce?

No. There’s compelling scientific evidence that Varroa levels in hives on small cell foundation may actually have higher mite levels than those on standard foundation. These are from properly conducted and controlled studies involving dozens of hives.

It certainly is claimed that mites struggle to reproduce in small cell foundation. The evidence actually directly contradicts these claims. Undoubtedly beekeepers in the USA have reported encouraging results, but scientists doing side-by-side comparisons clearly demonstrate that mite levels are at best not changed or at worst appreciably higher on small cell foundation.

Actually, it’s not the mites but our bees that struggle to reproduce in small cells. This explains the phrase “subject to regression over a period” above. You have to select smaller bees that can reproduce well in small cell foundation. Once this is done, the bee size is measurably smaller and the density of brood cells in the hive is greater.

Is this is a one-off study – where is the independent verification?

No. They were repeated at least three times by labs at the University of Georgia. Similar studies were conducted by Florida Department of Agriculture and Consumer services. In addition, the Ruakura Research Centre in Hamilton, New Zealand, conducted their own study – using a different experimental format – but achieving the same conclusions. Small cell foundation increased mite levels when compared with conventional or standard diameter foundation. There are now several additional independent studies which essentially reach the same conclusion – small cell foundation does not restrict Varroa replication and may actually increase it.

Has this new research been published?



After all, perhaps Thorne’s aren’t completely up-to-date about these studies? If the work is really new then perhaps they can be excused for trying to flog something for which there’s no compelling evidence of benefit.

Well, it was published … in some cases seven to nine years ago:

  1. Taylor, M.A., Goodwin, R.M., McBrydie, H.M., Cox, H.M. (2008) The effect of honeybee worker brood cell size on Varroa destructor infestation and reproduction. Journal of Apiculture Research 47, 239–242 … summary, a higher proportion of cells from small foundation were mite infested.
  2. Ellis, A.M., Hayes, G.W., Ellis, J.D. (2009) The efficacy of small cell foundation as a Varroa mite (Varroa destructor) control. Experimental and Applied Acarology 47, 311–316 … summary, no difference in mite levels between small cell and conventional foundation.
  3. Berry, J.A., Owens, W.B., Delaplane, K.S. (2010) Small-cell comb foundation does not impede Varroa mite population growth in honey bee colonies. Apidologie 41, 40–44 … summary, small cell colonies had ~40% higher mite infestation levels when compared with conventional foundation.
  4. Seeley, T.D., Griffin, S.R. (2011) Small-cell comb does not control Varroa mites in colonies of honeybees of European origin. Apidologie 42, 526-532 … summary, no difference in mite infestation levels between small cell and conventional foundation.

If you want an accessible and readable account of small cell foundation studies Jennifer Berry has written one for Bee Culture which includes experimental details of the work in references 1-3 above.

In denial

A recent thread on Beesource discussed the reported benefits of small cell foundation and the scientific evidence that contradicts these claims. It’s notable that supporters of small cell foundation generally criticise the ‘agenda’ they claim scientists have, rather than providing scientific evidence that supports the ‘benefits’. I’ve not been able to find a single peer-reviewed and properly controlled study that supports the beneficial claims for small cell foundation.

Hives on small cell foundation may have manageable levels of Varroa. If they do it’s in spite of the use of small cell foundation, not because of it. I am very willing to accept that there are some very competent beekeepers using splits, rational miticide treatment or other strategies and small cell foundation, who have low or manageable Varroa levels. However, it’s their beekeeping skill and experience not the choice of foundation size that is important here.

Indeed, you could argue that the detrimental enhancement to mite reproduction of small cell foundation, means that they must have truly exceptional beekeeping talents.

Or an agenda perhaps 😉

Ambiguous and misleading titles

In the opening paragraph I stated that the title 4.9 mm foundation for varroa control” was ambiguous. The scientific evidence presented above is that small cell foundation does control Varroa. Assuming you use the word ‘control’ when defined as the power to influence or direct the course of events. Small cell foundation does exert control … but almost certainly in the opposite direction to the way implied in the title.

What turns an ambiguous into a misleading title is this implication that small cell foundation reduces Varroa levels. The text that accompanies makes this implication without providing any sort of balanced view based upon the published evidence to the contrary.

Beekeepers, particularly beginners, looking for effective ways to reduce their mite levels are not being provided with the facts and are likely to be misled.

But wait … were all these scientific studies flawed?

Thorne’s partly justify the sale of small cell foundation in their newsletter by citing a UK research project that involves its use:

“The University of Reading has just started an exciting new research project examining the highly problematic issue of varroa mites and whether the use of small cell foundation (4.9 mm) can help. This is being carried out with volunteer beekeepers in the local area as well as in an apiary at the University. The study will evaluate the use of small cell foundation alongside regular-sized (5.4mm) foundation and compare the varroa loads during next spring and summer.

This is an interesting topic to research as beekeepers around the world have had success with the use of small cell foundation whereas many others have not. Some previous studies have also found that varroa counts increase in the short term when small cell foundation is first used. The new study will evaluate what happens once the bees have fully adjusted to small cell foundation and if there is a significant impact on varroa loads.”

The implication here is that the previous studies (above) are flawed because they failed to use bees that were properly adapted to small cell foundation. Thorne’s do clearly state that the bees have to be properly adapted – subjected to regression – for several months before benefits are seen (or claimed to be seen). To their credit also, they acknowledge that some studies show increases in mite levels. This text is from the newsletter and unfortunately does not appear on the webpage of their catalogue that describes the foundation.

Call me sceptical …

If it looks like a duck ...

If it looks like a duck …

As you can tell from the tone of this post, I remain sceptical.

If it looks like a duck, if it swims like a duck and if it quacks like a duck … it is a duck. As a scientist I’m influenced by controlled studies, not hearsay or beliefs.

The Berry study (ref 3 above) did use bees reared on small cell foundation for their comparative studies, the other studies did not as far as I can tell. However, remember the original hypothesis about why small cell foundation is beneficial. The mites do not develop properly within the cell as they are ‘crowded’ by the abdomen of the developing honey bee pupa i.e. there’s too little space for the mite.

What does regression lead to? Smaller bees. In the Berry et al., study the weights of adult bees reared on small cell and conventional foundation was 129 and 141 mg respectively. This seems to be contradictory … if properly regressed bees on small cell foundation are significantly smaller than those on conventional foundation how is the space for the mite development restricted? I acknowledge that the cell size is proportionately smaller than the reduction in adult bee weight. Conversely, if small cell foundation is supposed to restrict mite development, why are levels apparently higher when ‘normal’ sized bees are first forced to use smaller cells? Surely there should be a greater reduction in mite reproduction before the bees have regressed?

I hope the study being conducted by the University of Reading is thorough and properly controlled. These are difficult studies to conduct, particularly at the scale needed to be statistically convincing and when not under the direct control of a single beekeeper in a single apiary. I wish them every success with the experiments and look forward to reading about it once it is peer-reviewed and published.

Until then I suggest you save your £11.60 for ten sheets of small cell wired brood foundation … you’d be far better off preparing foundationless frames and controlling Varroa by rational and judicious use of hive manipulations and approved miticides.

Additional reading (far from exhaustive):

The late and still unbeatable Dave Cushman has an article by Philip Denwood reproduced from the 2003 BIBBA magazine on cell size. Recommended for a historical perspective.

A 2013 article from the New Hampsha’ Bees blog Small cell doesn’t work (but please don’t tell my bees describing typical evidence that small cell foundation does work … anecdotal and not controlled, but nevertheless enthusiastic and – unusually – acknowledging the evidence against.

Michael Bush on small cell bees and foundation.

Dee Lusby – one of the originators of the ‘small cell’ movement – in an early article from ABJ reproduced on the Beesource forums. Be warned … there’s some misleading nonsense in this article. For example “it is a known fact that both honey bees and mites have been on this Earth many millions of years together and survived quite nicely”. I don’t disagree that both mites and bees have been around for millennia. However, they have only been together for a century or so. I think I’ll have to write something about natural beekeeping in the future …

It’s notable that top Google ‘hits’ for small cell foundation provide no scientific support for the claims that are made … caveat emptor.




8 thoughts on “Small cell foundation

  1. Emily

    Thanks for writing this. It’s puzzling why some beekeepers are so keen on small cell despite the lack of evidence to support it. I wonder if the reason is that it seems like an easy fix – chemical free, relatively cheap and simple to use. If only it worked!

    1. David Post author

      Hi Emily
      I think some underestimate the damage that Varroa and viruses wreak, resulting in turn in an underestimation of the strength of the intervention needed to control these parasites. I also think you’re right that things like small cell foundation are perceived as being more ‘natural’ and that there’s an aversion – wrongly in my view – about using chemical interventions or other more robust methods. Varroa is, in evolutionary terms, a new threat to honey bee health and one essentially created and propagated by beekeepers. As with other host/parasite interactions a balance will be achieved over evolutionary time, but this is unlikely to be soon enough for current generations of beekeepers to benefit from and may well lead to the emergence of bees that are totally unsuitable for beekeeping.

    2. Jeff Randall

      Sorry for this terribly late comment on your Small Cell Foundation article. If the hypothesis is that the varroa mites are crowded out in small cell comb as you state, then maybe the scientifically based studies are not asking or testing the correct question; or not running the trials long enough (ie. over more than one season; or ???. I haven’t seen any studies that look at the effect caused by small cell workers and drones having shorter brood cycles and how that affects varroa mite reproduction and reproduction numbers. Seems like a promising research topic to me.


      1. David Post author

        Hello Jeff
        At least one of the studies I cited did use bees properly regressed onto small cell foundation. If the bees are smaller and the development cycle shorter then the expectation would be that less Varroa would develop. However, this isn’t what’s observed. I think the reference I made to a study at the University of Reading might provide more information, but have heard nothing more about it.
        The ‘bee size’ issue I address in the post … regressed bees are smaller, so the space available for the mite in the cell should not be reduced, when compared to a non-regressed bee on small cell foundation.
        If a proponent of small cell foundation did a properly controlled study demonstrating (in a statistically convincing manner) that bees on small cells had lower mite levels I’d be delighted to write something about it here. The problem is that – like many other ‘magic’ solutions – the only evidence is anecdotal or hearsay. Just because they want it to be a solution to mites doesn’t mean it is.

  2. geebee

    The thing that struck me was how the small cell size would increase the host density. Something known to drive increased parasite virulence. To me it makes complete sense that mite levels are higher in colonies that contain more sites for reproduction I.e. In colonies with a small cell size but the same brood area.

    1. David Post author

      Hi geebee
      Small cell foundation is known to increase brood levels and worker density, but not hugely (haven’t got the numbers to hand). Surely the key thing that’s relevant here is brood availability per mite. Mite levels would have to be extremely high for worker brood to be limiting. At those sort of mite densities the colony is probably a goner anyway. I don’t disagree that parasite virulence is related to host density – this is one of the justifications Seeley has for well-spaced feral colonies that are “mite resistant” (behaviourally, not when actually challenged I think). However, whether the worker density in small cell-based colonies is sufficiently increased to influence mite ‘virulence’ remains to be demonstrated.

      I don’t think I’d want my colonies anywhere near the hives it was being tested in though 😉


  3. Mikey B

    As someone who has recently taken up beekeeping, I find it fascinating that there is a polarisation of opinion whenever a controversial topic is raised. I found your article very interesting, and this article also to be interesting (, not so much from the point of view that Varroa can/cannot be controlled by small-cell foundation, but that there is such a difference of opinion across beekeepers.

    I’m puzzled, however, at the vehemence against the use of small-cell (4.9mm) foundation (especially, as I understand, this is a naturally occurring size in wild bee colonies – do they read these articles, I wonder?).

    My inclination is to consider other factors – for instance I was at a bee talk recently where the speaker (a respected National Beekeeper, but will remain anonymous here) mentioned that the small-cell foundation works at reducing varroa destructor infestation, not because of small cell size (and restricted space), but because of reduced development time of the bee (from 21 days to 20 days) in becoming adults. In theory, this reduces the opportunity for the varroa mites to develop. The claim is that at day 20 the adult bee emerges and the second daughter of the varroa mother is still in an unsclerotized state and dies (as they need the 21 days to fully develop) – thus reducing increased population.

    The other aspect of this is maintaining brood chamber temperature which apparently assists in the shorter development time of the adult bee.

    So I think much more research needs to be done before we can simply make a decision for or against the use of small-cell foundation.

    Whilst I appreciate scientific studies show that there is no significant difference to varroa control in small-cell foundation, I shall keep an open mind (and an open Google page) as to research. The article suggested above is 2017. I look forward to further research, so that we can better understand the ways of the complex and fascinating creature known to us as the honey bee.

    1. David Post author

      Hello Mikey

      I think there are a number of problems with these types of “controversies” … an idea is proposed, tried by one or many beekeepers and becomes popular. However, almost none (or none at all) of these ‘tests’ is rigorously or scientifically conducted. Controls are missing, significance is ignored etc. When investigated by scientists – and published in the sorts of papers I cited in the article above – there is no significant benefit. This happens time and time again. Small cell, electromagnetic waves, ley lines, sound emitting boxes under hives etc etc etc. Yes, it makes sense that shortening the development time might reduce the levels of Varroa (after all, the longer development time of drones accounts for the greater yield of Varroa from these cells). However, I’m not aware that this has been formally shown … after all, the bees are smaller, but they still have to develop legs, wings, antennae and eyes, all of which takes time. Let’s assume the one day reduction does reduce the mite yield. By how much? For it to be convincing it needs to be shown that a) small cell really does reduce mite levels, and b) that the average yield of mature mites from small cells are reduced.

      I’m a scientist and I therefore have a biased view on ‘proof’ and what it takes to make a convincing case. I wish those who propose things like small cell conducted a properly controlled experiment that would stand up to proper peer review and academic scrutiny. I would love to have a way to reduce Varroa loads in my colonies. However, nothing I’ve read convinces me it’s worth trying and I neither have the time or money (or enthusiasm) to do the experiment myself.

      You should keep an open mind. Everyone should. Mine is open. However, I’ll only believe some of the claims I see (for small cell and the myriad of other ‘solutions’, all of which appear to have a perfectly sound – though of course usually untested – explanation) when they are tested properly, reviewed independently and repeated successfully.

      Small cell, when investigated in this way, has yet to be shown to be beneficial as far as I’m aware.

      Many beekeepers want a quick fix that solves Varroa, they want an organic or treatment-free remedy that magically makes their hives healthy again. Varroa is a man-made problem for beekeeping, caused by beekeepers and not helped by current beekeeping practices.

      The current ‘best’ solutions are quick, inexpensive and – if you want – organic. But they require chemical treatment at the correct time, they require a good appreciation of the replication cycle of the bee, the mite and the influence of the season on the colony. They can be hugely aided by excellent interventionist beekeeping techniques – shook swarms, enforced broodlessness – all of which need a certain amount of skill.

      Bees are fascinating. I love keeping bees. I particularly enjoy keeping healthy and productive bees. I work reasonably hard to achieve this. I expend this effort in using methods – beekeeping and treatment – that are proven to work.

      Scientifically proven, with high levels of statistical significance …

      Maybe someone will come up with a small cell study that meets these criteria. If they do, I’ll certainly be writing about it.


      PS I’m in the process of switching servers. This comment may be lost in the process. However, I have a draft of an article for the future on the subject of the difference between compelling scientific evidence and wishful thinking. Thank you for your comment (which I’ll try and transfer across). It’s an important topic – more philosophy that beekeeping per se – but, hey, it’s the winter and we’ve got time to philosophise a bit 🙂

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