Ventilation of the beehive by honey bees

Do honeybees form ventilation lines for effective cooling, dehumidification or gas exchange?

In a natural beehive in a tree cavity there are no significant natural air changes. Ventilation with the aim of gas exchange, cooling or dehumidification must be actively performed by the bees. It is known that honey bees start fanning when air temperature, CO2 and relative humidity rise above the level for comfort. Not known – at least I haven’t found anything about it in literature – is wether and how they coordinate ventilation of the beehive. If each individual bee would start to fan in any direction when exceeding the respective limit value, then no effective flow pattern would develop within the honeycomb structure. There would rather be many diffuse air flows which partly work against each other.

It would be reasonable and much more effective if the fanning bee would at the same time give a signal for the flow direction and if this flow direction would then be maintained by the following bees. This would create a ventilation line. When the airflow hits a barrier (cave wall), the airflow is naturally deflected by the barrier at an angle that is as flat as possible, and the airflow (including its smells) is directed along the cave wall. If the bees were to maintain the given air flow as well as possible, the air flow would quickly arrive at the lower edge of the honeycomb structure.

And this is exactly what the honeybees seem to do with the opening of the Nasonov’s gland when fanning. In the past I have taken IR pictures of fanning bees in different areas of the hive. All bees filmed inside the honeycomb structure have opened the Nasonov’s gland when fanning.

Possible function of a ventilation line to dehumidify the hive

  • a bee in the brood area begins to fan, trigger is high air humidity
  • the relative air humidity increases in the direction of flow, also through cooling of the air
  • another bee begins to fan, the flow direction is known and is maintained
  • the ventilation line is carried on to the lower honeycomb edge
  • condensation occurs below the honeycomb structure and water is removed from the air. It now slowly flows upwards again, is warmed up by the bees and has a lower RH than before.

fanning bee with open Nasonov’s gland high up in honeycomb structure
further fanning bee with opened Nasonov’s gland

Fan at the lower edge of the honeycomb structure. After about 4min she changes position (at higher resolution the flapping of the wings can be seen very well)
many fanning bees on the cavity wall on the left, at the height of the lower edge of the honeycomb structure