16 May

Determining the optimal drone biomass with respect to swarm control

As an illustration, let’s choose a colony of about 60,000 worker bees, producing a swarm of 3 kg. In our swarm control we will offset the biomass of a 3 kg swarm of bees, not the half that would remain in the colony during potential swarming. It is important to realize that swarm worker bees are soaked, and based on the degree of soaking, the 3 kg swarm may consist of 18-20,000 bees. If we count with the weight of 0.15 g per one swarm worker bee, then the swarm will consist of 20,000 bees.

This means that the biomass of 13,043 drones needs to be first divided by two. This will ensure that we offset just the swarm bees, not the hive bees. We get 6,521 drones. Considering the stable reproduction strategies of the worker bees, this number is the amount of invested energy equivalent to the same swarm biomass of 3 kg. It is precisely the same amount of drones that a wild colony would raise in one season without human intervention. The same amount would be produced on the area of 6.52 dm2 of drone comb brooded from both sides. It is a smaller area than the area of one Czechoslovak frame, which is the frame size I use, with the area of 9.8 dm2. For our swarm control purposes the number 6,521 needs to be further multiplied by 4.5. Only then will the drone biomass be equivalent to the biomass of a potential swarm, not only in terms of energy investment on the part of the worker bees, but also in terms of their genetic benefit. The conclusion then is that a swarm of 3 kg can be replaced with continuous production of 29,344 drones. This number can be rounded up to 30,000. Because a swarm of 3 kg is by far not the maximum! Raising 30,000 drones will offset in all respects 20,000 swarm bees, comprising a swarm of 3 kg. The number of drones is then 1.5 higher than the number of worker bees in a swarm, 4.5 times more energy is invested in them, and they represent equally valuable biomass for the worker bees in terms of genetics.

An area of 1 dm2 takes unilaterally 247-250 cells of drone comb. Let’s work with the number 250 for further calculations.

30,000 / 250 = 120 dm2.

The combs are fertilized bilaterally, so we need to divide the number by two:

120 / 2 = 60 dm2 of drone comb

The inner dimensions of the Czechoslovak frame that I use are 35 x 28 cm. Its area is therefore 980 cm2 (9.8 dm2)

60 / 9.8 = 6.12 frames.

And this is still not the final number. We need to realize that the production of drones is a continuous, not a one-time process, and the drone comb will be fertilized by the queen at least twice. We will therefore divide 6.12 by two. The result is 3.06 Czechoslovak frames, which can be rounded off to 3. So far we have talked about a swarm of 3 kg. However, swarms of up to 6 kg have been known. Therefore, in colonies that rear brood in multiple hive boxes we sometimes need to increase the area of drone comb proportionally. This concerns in particular colonies with two queens or strengthened by divides. It is also necessary to take into account that building frames are never fully brooded across their entire area. Therefore, it is better to have the bees build one more.

Here the mathematics ends and my long-standing experience takes over. Here I declare publicly that if a naturally led colony with a single queen has got in the centre of its brood nest a drone comb area equal to the area of four Czechoslovak frames, i.e. 3,920 cm2 (608 square inch) it will not swarm under any circumstances. In the case of exceptionally strong colonies or colonies strengthened by divides, it is better to apply 5-6 building Czechoslovak frames or their equivalent.

I know that the Langstroth frame size is predominant in the world and that there are dozens of other national frame sizes. It is necessary that each beekeeper calculates, using the above-described formula, how many frames of their size they will need for swarm control drone rearing. I am sure it will cause no problem.

2 thoughts on “Determining the optimal drone biomass with respect to swarm control

    • Thank you for your question, John. If the area of your frames is at least 3920 cm2, it will work for sure in two brood suppers with a couple of drone brood in each. Bees will not swarm.
      As for plastic Drone Comb for Varroa Control, we consider drone cutting as not sufficient for improving Varroa situation. It lowers absolute number of mites in the hive, however it put much higher pressure on worker bees after the drone combs are removed. If the drones are present, they protect worker bee population, because majority of the mites focus on drones. Worker bees are therefore almost without mites, even if the number of mites in the hive is quite high. So we have completely different strategy how to deal with the mites – let them focus on drones, limith their numbers with slight thermal support that prevents repruduction of the mites and than eliminate the rest of them with thermosolar treatment after the drone rearing ends.

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