# Winter Carbon Dioxide Measurement in Honeybee Hives
## 4 Discussion  
Honeybee colonies act as a superorganism [48; 49], and one aspect of this is associated with thermal regulation, which maintains the brood area between 30 \({}^{\circ}\)C and 35 \({}^{\circ}\)C. Each individual bee responds to the local temperature environment by either isometric contractions of her flight muscles to generate heat or fanning her wings to draw in cooler air [50; 51]. Temperatures below 15 \({}^{\circ}\)C can induce clustering centered on the brood areas. It was reported by [PERSON] [15] that a response to extreme levels of carbon dioxide is fanning. One aspect of fanning is to help evaporate the water off the nectar stores to safely store it as honey. However, we know that fanning is thought to be used to regulate the temperature inside the colony by circulating air through the hive. In the winter, this will result in cooling, particularly where the air being drawn in is very cold. While the data showed that the temperature fell as the carbon dioxide level was reduced, this also tracked the outside temperature so cannot be directly or fully attributed to the fanning behavior. However, this does suggest that there are at least two competing mechanisms at play in the hive at low temperatures, with outer bees in the cluster expending energy to reduce the CO\({}_{2}\) while the inner bees try to generate sufficient heat to maintain the brood temperature against this increased cooling. This raises the question of whether the design of hives can be made to reduce this expenditure of energy and improve survival rates. The use of wooden boxes as beehives became mainstream after the 1850s, when [PERSON] discovered the \"bee space\" and revolutionized modern beekeeping [52]. He found that bees would not build a comb in a space tighter than 1 cm. His brood box used hanging-bar removable frames spaced exactly 1 cm apart and 1 cm from the box walls. This is still the main design used today, with Langstroth hives remaining popular, but alternative options with different sizes include the British National hive and the Dadant. Lightweight polystyrene versions of the basic brood box are also available, which improve insulation and reduce the effort of the colony in temperature control. These are still basic boxes with the use of supers on top and do not provide any further sophistication in ventilation. We know that the temperature in the upper supers gets close to the outside temperatures, so the incorporation of trickle  
Figure 7: The CO\({}_{2}\) in ppm (black) and temperature (blue) for the queen excluder in colony HPP7 starting on Tuesday 6 December 2022 at 11:48. (**a**) The data shown for over 140 days and (**b**) a close-up of the same data for the first 35 days.  
vents to improve the air flow may not affect the overall hive temperature profile but may improve ventilation. An alternative would be to provide warmed air drawn through the hive when the CO\({}_{2}\) levels rise above a certain level and the outside temperature is low. It is usually the case that the bees 'know best' how to look after their own environment, but in extreme cold, human intervention may well save colonies.