URGENT ACTIVE HEATING OF THE NEST.

Reinforced convection heating, the task of which is to quickly restore the temperature in the hive, which is necessary for the active work of the bees, or for brood rearing. In spring and summer, its presence is usually associated with a large number of sealed brood, and sometimes with the presence of queen cells. In winter - with a sharp cooling of cluster of wintering bees.

The existence of this type of heating was assumed by us for a long time, but unfortunately we did not have enough observations to confirm this effect. Some data from our summer observations and from experiment conducted in winter time allowed us to confirm our ideas. What is the meaning of our idea .... The point is, that for heating of a large volumes as quickly as possible, or for fixing some kind of emergency situation, there is needed the most efficient method of heating and transferring of heat. This is convection, which, in combination with heating of the bee itself, can provide the fastest heating of the nest, the wintering bees' cluster, or the hive as a whole.

The use of this heating method in conjunction with the other three known methods - heat insulation, passive heating, active heating with generation of vibro-acoustic signals without movement of the wings, allows not only to maintain the temperature in the most economical way, but also to eliminate the consequences of emergency situations. In addition, the work of the bees, as an active process, is also accompanied by the release of heat. This is not a heating method, but this process participate in the overall picture of creating and maintaining heat in the nest too.

What exactly the mechanism of urgent heating is ...  We assume, that in addition to silent heating, and heating with thorax vibration, exists the type of heating, which use wings flapping as a source of heat generation. This mechanical loading reduces the resonant frequency of vibration of the muscles of thorax, but increases the amount of work done, as a result,  producing more heat. This also improves heat removal and provides forced convection, redistributing the heat in an optimal way over the volume of the nest or in the winter cluster.

Why is it better to flap wings with a frequency of about 100 Hz, than to vibrate with a higher frequency? Or why not to flap wings with a frequency much more than 100Hz?  It is thought because in all cases Nature avoids the waste of energy and life resources. Unfortunately, any living being is not forever. Each has its own resource. And everyone save and cherish it, lengthening their lives.

And what about vibrations and flapping of the wings? In order to understand this, we will give an example: When we freeze, we begin to shiver. Muscles vibrate, producing heat. If this does not help and we continue to freeze, then the shiver becomes stronger ... we just start to shake. Muscles begin to perform even more work, releasing more heat. But the surest way to quickly warm up in the cold time, is to start waving hands and running. So, our muscles make more work, and  produce more heat. Further, our internal convection starts working. Yes, and we have it too. Convection of blood begin to transfer heat to our internal organs, warming them. We get warm, stop shivering, and stop running and waving our hands. Our body warmed up and went out of the critical phase of cooling.

Realizing that we all have a single Creator, we draw a direct analogy, believing that the general algorithm for the functioning of living beings is one and the same ... And the bees act quite similarly to us... When it become cold, bees  begin to strain muscles, producing heat without vibration. By the way, we are also know how to do it ...  If this does not help, the bees begin to vibrate, emitting more heat, thanks to the accomplishment of more work. If this does not help, then the bees begin to flap their wings, as we do with our hands... By doing more work, they achieve production of more heat! Moreover, in the result of these actions, the bee blows on her own body, and on everything that surrounds her...

 What is the reason for the importance of such a blowing ... The reason - is the efficiency of heat transfer ....

We have no doubts about the effectiveness of  convective heating. Convection is a process of heat transfer during moving of volumes of liquid or gas (fluid) from the place with one temperature to the place with another temperature. In this case the heat transfer is inextricably linked with the transfer of the medium itself, which is essentially a heat carrier.

Convection of heat is always accompanied by conduction of heat. The joint process of heat transfer by convection and conduction is called convective heat transfer.

The intensity of transfer of heat( or cold ) from one medium to another is characterized by the transfer coefficient, which depends from each environment. If environments have dramatically different coefficients of heat transfer, the heat transfer rate is determined by the environment, which makes it the most slowly.

What else affects the intensity of heat transfer. Of course, it's the relational speed of movement of one media over other. As you know from the basics of heat transfer, the heat transfer coefficient increases with increasing of the speed of heat carrier, in our case air flow. But not indefinitely. There is an optimal ratio of speed of air flow, relative to the stationary environment, which is characterized by maximum quantity of the transmitted heat, with expenditure of optimal amount of energy to move the heat carrier. In our case, the two environments are - the body of the bee, and blowing air. If you will use forced blowing of solid body by air flow, instead of free convection, then heat transfer coefficient increases twice.

Additionally, the heat transfer depends on the shape and geometry of the body, blown by the air. The larger the contact area of solid body with air flow, the higher heat transfer. The less streamlined is the shape of the solid body, blown by the air, the higher the coefficient of heat transfer.

In all these, bees are not too much lucky. Their streamlined body covered with a chitinous exoskeleton is not the best heat exchanger. This means that the rate of heat transfer from the body of bees to the air flow will not be very high. So, the flapping of the wings provide air flow, removing heat from the body of bees and transferring it to the brood and other parts of the nest can't be very high. And frequencies rate of emitted sounds can't be very high.

Such sounds with the frequencies above 20 Hz. people can hear as a very low sounds, and our device can register them, if their frequencies are higher than 70 Hz.  And indeed, our device captures such signals at times of tense situations in the bee family. The frequencies that we fixated, were in the range of about 100 Hz and by the type of picture of the spectrum could be attributed to the signals, created primarily by bee wings, since they have the correct multiplicity of harmonics x2, x3 ... etc.

And how do the  bees use their heating capabilities at different situations of their life ...

Settling into a new home, the swarm immediately begin to maintain the temperature, necessary for the beginning of egg laying by the queen. Then the bees begin the process of maintaining the temperature using thermal insulation and passive heating of the nest. Further, if it is necessary to maintain the temperature in a larger volume, the bees use  additional active heating. In cases of a sharp drop in temperature, the bees immediately use urgent heating. After restoring the temperature balance, this type of heating stops and the bees go over to more economical forms of heating.

Let's consider the examples of our observations, which we believe, confirms our ideas...

Recently, we conducted an experiment on cooling the nest of hibernating bees with the fixation of changes in the background signals in the hive. The results were very interesting. At the outside temperature of -15C , we received data, possibly confirming our hypothesis about the "conditioning" of the hive, that is, the use of ventilation of lowest force, in order  to improve the heat removal from the bee's body in emergency moments of severe cooling of the nest ...

We assumed that in addition to heating, which is usually silent, heating with the performance of flapping of the wings can be used by the bees. This reduces the resonant frequency of vibration of muscles of thorax of the bee, but adds improved heat removal and provides forced convection.

When we removed the warming pillow and left only a thin fabric, separating the upper part of wintering bees cluster from the street and made measurements, we saw how the signals characteristic for various jobs in the warm nest began to change, and turned into signals of the lowest frequencies ventilation,  and thorax vibrations which in sum provide the best heating and convection of warm air.

When the pillow was returned, after 20-30 minutes, the signals changed again, and began to correspond to the performance of in-hive works and feeding... We managed to simulate this situation two times in a row. The predominant signals were - heating and convection.

Further research conducted using our archives, showed, that this situation is not unique. The same signals were recorded in the summer in a very specific situation. This once again confirms the immutability of the principle of life support in bees, and its independence from the season of the year.

The appearance of the signals, was absolutely similar to our winter urgent heating, but was recorded in June, in the family, in which there was sealed brood and queen cells.  And we already expected a close exit of the first queens. It should be noted, that at this time, in June, it was pretty cool. The bees in the hive were less than they needed, because these families, in which we were waiting for the queens, were practically divided in half. Thus, the number and age composition of  bees in these families did not allow them to use passive or active heating. And the bees used the most efficient method of heating - heating with convection or as we called this effect - "urgent heating with convection".

As another confirmation, can serve an experiment, in which was used our  observation hive, which we moved from sunny outdoors place to the cold room. In this situation, when the bees placed on the frame with sealed brood  felt cold,  they shifted from the passive state to active ...  At first, they made attempt to retain heat, and then they shifted to active heating and urgent active heating. Here you can consistently see all the phases we talked about. And in the last phase, it seems to us, we can see the signals of both types of heating - of active heating and of urgent heating with convection.

Yes, unfortunately everything is not so simple. We do not yet know, whether there is a combined mode, when a bee can vibrate warming the chest, and at the same time, to blow on itself using her wings. Apparently, since the same muscles are involved in both modes, the bees cannot perform two types of work at the same time. But they can do it in turn! After all, the vibro-acoustic signals which were recorded by the scientists, were lasting for about 0.2 seconds or less. This means, that  for our eyes, a periodic change of heating process to flapping by the wings, will be not noticeable... But the device, based on the Fourier algorithms, will record two chains of pulses with different frequencies of the fundamental tone - one will correspond to the heating with the use of vibration of the thorax, the second will be created by heating with the help of wings flapping ! The possibility of this, we have to find out in our further researches.

There is another possibility that is much more prosaic. It is possible that in this situation we hear a few bees doing the work on heating the brood. But  one of them use "active heating", and the others have already switched to "urgent heating", considering, it seems, that it is better to overdo, than to freeze sealed brood.

it seems to us, that on the diagram it should look like this:

And only Apivox algorithms, after processing the signals for a long period of time, will determine the priorities in this mix of signals, and will give diagnosis about the state of bees, in correspondence with the average situation for the selected time interval.

 

Thus, we can once again state the presence of four modes of thermoregulation in bees.

- Performance of every-day in-hive works, leading to heat generation due to metabolic processes, and further heat preservation due to thermal insulation and creation of clusters.

 - Passive heating with virtually no any vibration of the thorax, but with the heating of the bee's chest.

 - Active heating with powerful vibration of  thorax and creation of vibro-acoustic signals in the low frequency zone of the working range, without the participation of the wings, which are fixed in slightly open position.

 - Urgent heating with the work of the muscles of the thorax in resonance mode, similar to ventilation, but in which the wings operate at extremely low frequency,   which leads to the development of the maximum amount of heat, and  creating a weak air flow, providing improved removal of heat from the body of the bee, and spreading it inside the hive.