I respect and appreciate Tom Seeley and consider him a friend. He coined the expression Darwinian beekeeping. He has given us deeper understanding of the natural bee colony. But I don’t understand an expression of his in one of his lectures in London Honey Show in 2011:
I don’t understand why beekeepers are so interested in small cells.
There are scientists that have expressed suspicion, yes even an opposition towards small cells (4.7mm – 5.0mm, large cells 5.2-5.5, extra large 5.6-5.8, average 5.1). Tests have been done with small cells. Focus has been on reproduction of the varroa mite. None of them has come with the result that small cells are bad for bees. The majority of them are expressing a result that is not statistically significant concerning a good influence on varroa resistance. But there are tests that show a positive impact on the varroa level, for example this: http://www.elgon.es/norwegian_celltest.html. Concerning the design of tests please read this analysis: http://www.elgon.es/testdesign.html
The classic picture by Dennis Murrell of a top bar with diffferent cell sizes. Those to the left are close to the entrance. An advantage with naturally built combs is that the midrib of the comb is very thin compared to a wax foundation. Therefore it’s easier for the bees to tear down combs and rebuild them as their needs changes. When a swarm starts to build combs they often start to build cells 5.3 mm big as their first need is to store the honey they are carrying in their honey stomach. Often they build quite some drone comb too. If it’s a first swarm and the queen is old they may well replace and then they need drones. Later when the nest is growing they replace some combs with new and build more honey storage away from the entrance (information from Johan Ingjald in Sweden who has studied this in his colonies).
When bees choose themselves, what cellsize do they make? They make a range of cell sizes. When we look at naturally built combs in colonies where wax foundation is not used, the brown (or black) wax, that’s wax in which there have been brood, the range of sizes is smaller than in areas where you find wax in which there have been no brood. In such areas bees store honey. See the picture of the top bar comb taken by Dennis Murrell.
What did bees build before wax foundation was used? Wax foundation started to be used more widely after the introduction of the waxroller mill in 1876 by A. I. Root in America (cell size 5.1mm, which was said to be the average of cellsizes in a colony). See the article about cell size history: http://www.elgon.es/naturalcellsize.html
The conclusion is that nature favors small cells in the brood area and larger in the honey storage area. After a thorough investigation the Harvard professor Jeffries Wyman published the result 1866 to be 4.7 mm – 5.3 mm for the cell sizes. The British scientist Thomas W Cowan replicated his test 1890 and got the result 4.7 – 5.4 mm.
Natural selection and fitness
Natural selection (adaptation) is what nature uses to adapt creatures to their environment. It’s one of the forces in the Darwinian theory (the theory of evolution). Sometimes this is called survival of the fittest. This includes not only survival, but those individuals that survive, are healthy, strong and not the least reproduce most efficiently.
The answer why bees want mostly (but not only actually) small cells in the brood area is obvious, isn’t it? The bee colony then is then better fit, survive better, is healthier, stronger and reproduce better. The question is not in first place about varroa resistance, it’s about fitness!
The result would be lower annual losses of bee colonies, whatever the reasons for the losses may be: pathogenes, bad managemant, chemicals, etc, wouldn’t it? The varroa mites don’t kill the bee colony by themselves, but through ”cooperation” with viruses.
There is a project presented in the Swedish beekeeping magazine – Bitidningen 2018, no 3 – called ”Varroaprojekt LEKA” (perfomed during autumn 2014 to fall 2017). It supports the conclusion that small cells in the brood area gives better fitness. A report of it may show up here on this blog.
Initially when varroa mites arrive to an area the mite population can become very big, regardless of the cell size in the brood area. If the bee colony does not die of viruses (it must be interesting to find out why that can happen!) it will adapt and lower the mite level with the help of different traits strengthened through adaptation processes (epigenetic and genetic), with the help of natural selection. See: http://www.elgon.es/diary/?p=1121
In the light of the above:
I don’t understand why scientists are not more interested in small cells.
There are more reasons for losses than large cells in the brood area. But why not minimize one obvious cause for bad fitness that we can do something about?
In Sweden the standard cell size now in practise is 5.1 mm. The use of 4.9 mm is increasing, 5.3 is diminishing. In Norway the situation is somewhat similar.