Brood nest temperature is of extreme importance to the colony and is controlled with utmost precision by the bees. This brood temperature regulation is called homeostasis. Honey bees maintain the temperature of the brood nest between 34°C and 35°C so that the brood develops normally. When the temperature in the nest is too high the bees ventilate by fanning the hot air out of the nest (which evaporates water) and sometimes even partially evacuate the nest.
Homeostasis can be used as a measure of colony fitness. More genetically diverse colonies (stemming from a higher number of different patrilines) are better at thermoregulation.
Brood temperature in your hive
When you have placed the sensor with the red sleeve in the middle of your brood frame, it will measure the brood temperature in your hive. Click on the hive icon and it’s ‘orange’ cell -icon, and the graph with the brood temperature will be generated.
This graph shows you the comparison between the brood temperature of two hives coming out of winter. The blue line shows that the queen started laying around 25th of Feb, and the brown line shows that the queen in the second hive started laying early March when the brood temperature became stable around 34C.
A drop in brood temperature
A drop in normal brood temperature, or even excessive variation in a day to day brood temperature is usually a sign that the bees are broodless.
There could be a number of reasons for a drop in brood temperature ;
- the colony may be queenless
- the queen may have stopped laying.
- alternatively, the brood temperature sensor may no longer be in the centre of the brood cluster as it migrates from side to side.
The example below shows you the brood temperature becoming unstable. Not until after a new queen was introduced in this colony did the brood temperature go back to 34C.
In winter, during brood-less periods, the temperature fluctuates with that of the ambient temperature but positively offset by the amount of heat generated by the cluster. This will give erratic temperature readings, but how much offset is achieved is an indicator of colony strength. Also, if the cluster is moving about in the hive, the centre of the cluster may not always be on the hive sensor. However you can see periodic peaks in brood temperature as the cluster moves across the temperature sensor.
Further information on this topic can be found in Arnia’s Whitepaper on Temperature and Thermoregulation.