WHAT HAPPENS IN A BEEHIVE ON A HOT DAY?
The male in the picture is obviously feeling
very hot. He’s sweating.
But what happens in a beehive when it gets
too hot?
The bee colony requires a constant
temperature in the hive of 35 °C, the
optimum temperature required for hatching Fig. 1: Sweating male and beehive in the sun.
the eggs and rearing the young. But how can a hive be cooled down during a hot day if the
outside temperature exceeds 35° C?
How is the beehive cooled?
What do you think?
Write down your assumptions:
The following model experiment should provide you with an answer:
You need the following materials:
Preparation:
clay pot, thermometer, hand fan, water
Soak the clay pot by putting it in water for at least an hour.
1.
Place the thermometer into the clay pot from above. Note the start temperature in the
table.
2.
Generate some wind with the help of the hand fan.
3.
Measure the temperature every 30 seconds for a total of 3 minutes.
time [min]
temperature [°C]
Fig. 2: Test setup with clay pot and hand fan
©
4.
Plot your results in a diagram!
5.
Analyse the result (based on the clay pot) in one sentence.
But what does it mean for our beehive?
6.
To answer this, it is necessary to compare the model with the original:
a)
What do the elements of the model represent?
model experiment
original
clay pot
hand fan
b)
What is different?
c)
What is missing?
d)
What is there in the model which the original lacks?
7.
Do the bees use evaporation of water to cool their hive?
The answer to this question was already described in 1945 by Landauer, a bee researcher:
„Water collector bees fill their bellies with water, return to the beehive, regurgitate small
drops and spread the drops on the surface of the honeycombs.“
Show similarities and differences between the model experiment and the observations by
Landauer.
8.
Another phenomenon can be observed on very hot days:
Bees stand in a line facing the hive entrance fanning
their wings to generate air flows.
But how is air circulating in the entire hive to cool it?
Prof. Jürgen Tautz has developed a model based on his
observations:
It can be observed that, instead of working constantly,
bees coordinate with each other to start and stop
flapping their wings at the same time. The progress Fig. 3: Fächlerbienen vor dem Flugloch
could take place as follows: Since the hot air rises up inside the beehive and the entrance
hole is in the lower part, the “fanning” bees must work against the hot air’s ascending
force: By flapping their wings, they pull out hot air, thereby creating a suction force. Once
they stop flapping their wings, this suction force pulls in fresh air through the (already
moistened) honeycombs.
If this assumption was true, the model experiment would need be modified in the following
way:
Expansion of the model experiment
We want to verify whether the hypothesis by Tautz can be simulated by modifying our model
experiment.
The following materials are available: plastic pot with an opening at the bottom edge,
thermometer, stand (made out of staples/ paper clips) and cloths that fit in the pot; the
computer fan (creates suction).
9.
Plan an appropriate experiment: Outline the experiment, conduct the experiment and
write down your results in the table.
time [min]
temperature [°C]
Fig. 4: Advanced experimental set-up:
See description for the test procedure
10. What is not implemented in the model?
What do the BeeBIT data suggest?
Is the temperature in the beehive actually kept at around 35 °C on hot days?
11. First choose a beehive!
12. Observe the course of the outside temperature for a period of at least 3 months.
13. Select time periods when the highest temperatures are above 35 °C..
suitable beehive:
suitable time period:
14. Now show the inside temperature(s) of the beehive!
Observation
Explanation