How to prevent colony destruction due to heat or cold
What you will learn here
- Is it possible to prevent a situation where a hive occupied by bees freezes in the spring?
- Can this be solved with just good thermal insulation?
- Is it appropriate to heat a bumblebee hive and how to do it?
Last updated: 11/2/2022
Thermal insulation of beehives for bumblebees – an introduction to the issue
If you offer a hive to bumblebees, you also take responsibility for how the hive will protect its inhabitants .
It is not only about keeping parasites and enemies of bumblebees out of the hive. The temperature in the hive should also not fluctuate too much . If bumblebees live in a cavity in the ground, in a wall , etc., the temperature there is usually lower than the air temperature outside the cavity, but above all it is stable . Such a place will also prevent them from getting cold when the temperatures drop sharply, or from getting too hot on hot days.
It is quite complicated to create a similar environment in a man-made hive, therefore it seems optimal to place it indoors (see description of hive placement ). The solution where the hive is placed in a relatively stable environment of a garage/basement, etc. is unfortunately not available to everyone.
In the spring months , the temperature often fluctuates greatly and sometimes it gets very cold for a long time and, unfortunately, very cold .
The breeder has several options for how to respond to this:
- She leaves the nest in the hive to fate and nature
– bumblebee mothers can sometimes endure such a situation, but often they abandon the nest
– sometimes they become exhausted and die while warming the brood - He leaves the nest outside , but provides the mother with wort (honey-sugar dough or sugar solution)
– the mother has a source of energy and a better chance of handling the situation - He closes the nest at night and takes it to the temperature max 15C see
– but transfer is not an optimal solution
– in addition to shocks and disturbances, moisture also condenses on the walls of the hive (temperature differences)These options are described in more detail HERE
- It ensures passive heating of the hive
- but it must be a heating that does not endanger the hive = it does not overheat it, does not dry it out and does not cause sudden temperature changes
- but simple heaters without regulation are often not entirely satisfactory - It will provide hive heating with temperature control
– this solution should regulate the heating output within a specified range, with an accuracy of degrees °C.
In all cases the condition for success that the insulation is of high quality , well insulated and has sufficient thermal inertia to dampen temperature changes.
Extreme temperature drops in spring
A sleigh ride in a snowy garden
Photo: PG Gröbl (21/3/2020)
Why and how does the temperature in a hive change depending on the temperature of the surrounding air?
The temperature in the hive will always equalize with the ambient temperature , that's physics, but the question is how long ( how fast ) it will take for this to happen. The optimal hive should slow down the change in internal temperature and overcome the peaks until the ambient temperature returns to normal conditions .
No thermal insulation, no matter how perfect, will prevent changes in the temperature of the protected object /content. Thermal insulation is simply not heating/cooling, you have to accept that. In addition, an object enclosed in insulation can be opened for a moment and the temperature inside it will quickly start to equalize with the surroundings. Therefore, the thermal insulation system must also include sufficient mass that accumulates heat. This, together with thermal insulation, prevents rapid fluctuations in the internal temperature of the object.
Physics and the same rules apply to hives as for passive houses . Human housing is a really good example, they talk about so-called thermal comfort and thermal well-being . That is why passive houses are equipped with the best possible external thermal insulation , but inside they are supplemented with material in the form of an uninsulated wall/structure. This acts as a battery and, together with the thermal insulation, prevents rapid changes in temperature in the interior.
the hive (bumblebee) is small and often does not have a suitable structure . Therefore, it often cools down/warms up very quickly and that is not good. For example, if the hive cools down to the level of the surroundings during the night , it can be threatened by short spring frosts . Insulation can improve its properties and delay freezing - but not prevent it . However, the effort is not to make hives too heavy so that they can be manipulated.
We performed simple measurements and compared basic types of hives . Some of the findings surprised us. For example, how the temperature in a simple small-volume hive without insulation quickly equalizes with the ambient temperature . It basically copies the external temperature with a delay of up to one hour . Other hives also behave this way, but if they have good insulation and internal mass, the delay is 2 or more hours . Even this is often enough to overcome the spring frost before the spring sun warms the air again in the morning.
Our measurements
As evidence of the behavior of different hives, we present the internal temperature curves in different hives . We will describe the graph and measurements, here only a demonstration of the influence of external temperature on hives and differences in the change of internal temperatures .
You can see for yourself how the internal temperature changes over time , even with a static external temperature. The less the temperature in the hive fluctuates, the better . Therefore, it is necessary to pay attention to the thermal insulation of the hive , rather than heating, which in practice is used only a few days a year.
Graph 1 shows how the temperature in the hives increases depending on the ambient temperature.
Description:
- Top – outdoor temperature
- Then gradually hives with different quality of thermal insulation
- The lowest curve ( gray ) represents the startle with modifications , which we further describe HERE.
Temperature measurement kit
Photo: O. Hercog 2021
Graph 1 shows how the temperature in the hives increases depending on the ambient temperature.
Description and evaluation of results:
- Top – outdoor temperature
- Then gradually hives with different quality of thermal insulation
- You can clearly see how big the differences are between the individual designs
- the temperature changes fastest in a small hive (green curve)
- slower in a larger hive
- The temperature changes almost as quickly in a commercially available hive and in a hive with 20mm polystyrene internal insulation
- the slowest changes are represented by the gray curve and light blue – this is a shed with 30mm polystyrene external insulation and 25mm wooden walls inside the insulation – its description is HERE
It is complicated to ensure stable temperature conditions in a passive hive , unless you want to turn it into a "engine room full of technology", so it seems optimal to place it indoors - see the description of hive placement .
This solution, where the hive is placed in a relatively stable environment of a garage/basement, etc., is unfortunately not available to everyone.
The temperature in the hive will always equalize with the warm surroundings , that's physics, but the question is how long ( how fast ) it will take. The optimal hive should slow down the change in internal temperature and overcome the peaks until the ambient temperature returns to normal conditions .
Graph 1 – Change in temperature in hives depending on external temperature – temperature increase
Measured by: O. Hercog 2021
Graph 2 demonstrates the process of cooling the hive depending on the external temperature
Description and evaluation of results
- Little Ulek did not participate in this measurement
- It is similar to Chart 1, only in reverse order.
- Hives without thermal insulation cool down very quickly.
- Even a large, uninsulated bird equalized its internal temperature to its surroundings.
- A well-insulated shed cools down the slowest – its description is HERE
Physics simply is and will always work.
Graph 2 – Change in temperature in hives depending on external temperature – temperature drop
Measured by O. Hercog 2021
Heating in the hive for bumblebees
There is a seemingly simple solution with heating in the hive. In reality, it is quite complicated and there is no universal solution unless you regulate the heating power and thus control the temperature .
Inappropriately designed and used heating can damage the brood (overheating or drying out), endanger its inhabitants and destabilize the nest cycle . There is no point in heating the hive too much and unnecessarily activating the queen when there is not enough food outside. Such a situation does not correspond to natural conditions. Similarly, it seems that a very comfortable hive leads the nest to raise sexual individuals early , even in a smaller nest.
Heating without regulation is a big risk . The exception is a solution where the heating power is found to heat the hive structure and is in balance with the heating power and losses to the environment. Without regulation, however, even in such a hive the temperature fluctuates depending on the ambient temperature and does not provide the bumblebees with a natural environment. Fluctuation here means that the temperature in the hive is always X ° C above the ambient temperature and this may not always be good. This can be solved with a timer , manual switching , etc.
Every heater in the hive means a temperature jump upwards after switching on – easily by 10°C within an hour or downwards after switching off. We have measured different types of heaters and the results clearly show this.
Unless you have a proven (tested) solution that provides the best regulated heating that can prevent the hive from freezing to 0°C , we recommend not heating . Even if such heating is available, it should only be used when the hive is in real danger of long-term freezing .
definitely not advisable to put a heater in the hive that has a contact temperature higher than 35°C . Many people have purchased heating cables. However, according to the manufacturer, these have a surface temperature above 40°C and therefore do not belong in the hive . They can be placed at most in the partition wall of the hive, which is adapted by the manufacturer for this.
If you have a different/own hive , it is necessary to carefully measure and test how such a heater behaves and how the hive heats. It is therefore not possible to say that a heater with a power of x W is suitable for every hive, unfortunately it is more complicated. When you measure, do it carefully, in the right place and also measure the values over time. There is no point in measuring the temperature in the lining , it will be different in each place. It makes sense to measure the temperature in the space above the lining . You will also see how quickly the hive heats up . the heating power so that there are no sudden changes in temperatures (turning the heater on and off).
The heating can be controlled with a suitable thermostat . However, you should expect that the temperatures will still fluctuate around the set temperature (the space accumulates heat). If you control it with a timer, there will be a series of temperature changes.
Bumblebees PLUS recommend
- We are making efforts to improve the design of passive hives and their thermal insulation.
This is also worthwhile in times of high temperatures and sudden changes, when a good solution dampens fluctuations and allows the hive to maintain suitable conditions for as long as possible. - Provide the mother with food (nectar and possibly pollen) on cold days, but do not disturb her unnecessarily by interfering with the nest
- Don't freeze the hive unless you have a good solution
. Spring temperature drops can be solved in other ways. For example, by transporting the hive after dark , where frost is expected, to a place where the hive will not freeze , but will not overheat. The temperature in such a place should not exceed 10-15°C. - There is no point in heating the hive heavily when it is cold outside and the bumblebees cannot fly and gather food, these are not natural conditions.
It is more natural for the queens to wait in a state of reduced activity for the temperature to rise . Queens of bumblebees in a good hive with a sufficient amount of good lining can overcome short-term drops in temperature even without heating. - If you want to heat the hive, do it in a way that the hive does not freeze and if possible use a heater with a regulator.
Other links:
about the issue of thermal insulation and our measurements HERE.
You can find a possible heating solution with a heating plate and regulator HERE
Regulator in a box on the wall of the hive
Photo: O. Hercog 2021
Measuring temperatures in hives
Photo: O. Hercog 2021
Conclusion
As always, we have suggested several solutions and explained their pros and cons.
Choose a solution that suits you both in terms of difficulty and your approach to bumblebee breeding.
If you share your experiences with us, we will be happy to use them and offer them to others.