Some Beekeeping History
The honeybees that you typically see, or perhaps the honeybees that you used to see before they disappeared from your area, are or were most likely larger than nature intended them to be. Understanding why this is true requires a short lesson in beekeeping history. For thousands of years, man kept honeybees in hives called "skeps" (think Friar Tuck). A skep is basically a straw basket in which bees can build a wax comb nest from scratch; no frames and certainly no wax foundation. Bees would simply build what bees build naturally; different sized cells to suit different purposes. Worker brood cells would be smallest (about 4.9mm or smaller), cells intended for honey would be bit larger and cells intended for raising drones would be the largest of all.
In the United States, skeps began to fall by the wayside in the middle of the 19th century, with the advent of the Langstroth (framed) hive. Foundation was developed with one main purpose in mind; to discourage the raising of drones. Since males do not contribute to honey production and are, in fact, large consumers of honey, beekeepers found them to be a counterproductive nuisance. Although bees would still squeeze in some drone comb where they could find room, or simply build it right over the top of the smaller hexagons on the foundation sheet, foundation did and does work to reduce the number of drones in bee colonies.
At the beginning of the 20th century, nearly all commercially produced wax foundations had cell sizes of about 5mm. Soon after, cells were made larger. The gentleman most credited with enlarging the cells on foundation sheets is A. I. Root. The theory was that larger cells would allow developing bees to grow larger, and therefore be able to gather more nectar to produce more honey. The experiment worked and foundation sheets with cell sizes of 5.4mm became standard in the industry. All was well for the next 85 years or so, until the varroa mite arrived in the mid 1980's.
The Most Common cause of problems is solutions
During the past several years, some very bright individuals have begun to theorize that the larger cell size has played a role in colony collapses from varroa infestations. These theories, rather than being based on very expensive scientific studies, are based on common sense, or at least what should be common sense. Two factors seem obvious. First, larger cells for worker bees means more room for the varroa mites to breed, lay eggs and feed. Second, larger cells have extended the incubation period of worker bees from 18 days to about 19.5 days. Now, 36 hours may not seem like much, but when you consider that mites live only about 100 days, this would be equivalent to about 9 months for you and me. In the video, the narrator talks about a female mite becoming embedded in the bee's cocoon before ever laying eggs. He doesn't say so, but it seems that smaller cell size must almost certainly be the reason for this.
The bottom line is that there is every reason to believe that larger than natural worker bee cell size has given the varroa mite more space and more time to get things done, helping to doom our bee colonies. In the "normal" (that is, in hives that do not have worker cells larger than 4.9mm) scheme of things, it's believed that the cycle goes something like this:
New bee colonies or swarms have very low varroa mite populations and thrive easily.
Once drone production begins, the varroa mite population steadily builds up.
Varroa populations peak at an infestation rate of about one mite for every 15-20 bees.
Drone production ceases in autumn and successful varroa reproduction is reduced to a much lower rate. Most of the mite population becomes "phoretic", meaning nearly all of the mites living among the adult bees. The mite population begins to fall. In hives with screened bottoms, the numbers fall even faster due to mites falling off of the bees and onto the ground. It is at this time when powdered sugar treatments are most effective in bringing down mite populations.
By midwinter, the colony is almost free of varroa, although some low number of mites will surely survive.
Spring and early summer brings swarming season and the production of drones, starting the cycle over again.
How we get back there from here
Although there are a few packaged bee suppliers that offer natural-sized bees (raised on small cell, 4.9mm foundation) most offer bees that are artificially large. Although it's true that artificially large bees will eventually return to their natural size if allowed to build their own comb (a process known as "regression"), it can take a while. Nobody can say for sure how long it will take for your bees to regress back to normal since there are too many determining factors, but it will likely take at least a couple of years. Bees raised in large cells will build large cells. If bees raised on large cell comb are left to build their own comb without it, they'll typically build combs with slightly smaller cells (maybe 5.1-5.3mm). The generation of bees raised in these smaller cells will later build new combs with slightly smaller cells again, and so the cycle will continue until full regression is achieved. It is not at all unusual for regressed bees to build combs having worker cells that are 4.7mm or even smaller. If you want to use standard Warré or octagonal hives and just let your bees regress naturally, you can do that. As long as you are harvesting honey each year and only leaving two hive bodies for the bees to overwinter in, your bees will build boxes of new comb each year and each successive box will have cells that are slightly smaller than the one before, until regression is complete. You will need to monitor closely for varroa the first couple of years and use (preferably organic) treatments as needed. Many people have succeeded at regression using this approach.
Using small cell foundation is by far the fastest way to force the regression of large honeybees. Although it is somewhat complicated and costly, it is likely to be easier and less expensive than dealing with varroa infested bee colonies. "Small cell foundation" refers to wax foundation sheets with 4.9mm cell size. The disadvantage of using this approach is that it requires the use of a modified Warré hive. However, modified hives can be converted to standard hives after regression has been achieved, by simply removing the frames and replacing them with top bars. So if you want to eventually use standard Warré hives, you can still use this approach to get started; you'll just use the frames only once. You could also reuse the modified bodies and frames to regress a new bee colony in the future (after you have harvested these two boxes from the first hive). Modified Warré hive bodies can also be used as supers on standard Warré hives.
NOTE: If you want to remove the frames and use top bars only in a modified hive body, it is probably best if you also remove the metal frame rests by prying them loose with a flat screwdriver.
In order to regress bees using foundation, it is necessary to start off your modified Warré hive (as always) with two hive bodies. In the upper hive body you will place 5.1mm (intermediate) foundation sheets in 7 of the 8 frames. This is necessary to ensure that your bees will be able to build their first combs properly, since large bees often draw out small cell foundation with difficulty. In the lower hive body you will place 4.9mm foundation sheets in 7 out of 8 frames. By the time the bees start drawing out the foundation in the lower hive body, there will be a large population of smaller (natural size) bees in the hive and they will be able to draw the small cell foundation without too much trouble. Leave the third frame (doesn't matter which side) in each box foundationless. Watch this video to see how to set up your frames. You can also wire the blank frames to give them extra strength. These frames will serve two purposes; the blank in the upper box gives you somewhere to place the queen cage upon installation of a bee package, and they both give the bees room to raise drones.
After your bees have drawn out the top box, they will start drawing out the bottom one. Take a look up through the screened bottom every few days to monitor their progress. Check in the early evening to see if the bees are clustering in the bottom box. Once you see that the bees have indeed began to cluster in the bottom box, it's time to enlarge the hive. Failing to add space for the bees will likely lead to swarming. At this time, regression can be considered complete, so how you proceed from here is totally up to you. If your goal is to have regressed bees living in a standard Warré hive, you can add one or more standard Warré hive bodies to the bottom of the hive. If you wish to continue using a modified hive, you can, of course, add one or more modified hive bodies with frames to the bottom. You don't have to use foundation anymore if you don't want to. But if you do, make sure you continue to use 4.9mm foundation.