Ventilating
Verhalten der Bienen
The colony keeps its brood nest at about 35 degrees, regardless of the weather outside.
The colony keeps its brood nest at about 35 degrees, regardless of the weather outside. Heating is done with the flight muscles. Cooling is done with water and air: the bees spread droplets of water on the combs and fan their wings so that evaporation carries away heat. On hot days a row of fanning bees can therefore be seen at the entrance.
The water requirement for this is considerable. According to the Berlin Institute for Bee Research, 40,000 bees need about 40 grams of water daily, and 6,000 brood cells need a further 140 grams; for 180 grams, around 18,000 flights to the water source are needed. The same technique serves honey production: to produce one kilogram, the bees bring in about 2.7 liters of nectar and remove around 1.7 liters of water from it. Ripening the honey in the colony takes about three to seven days.
In winter this is reversed. Then the colony sits as a cluster whose outer surface is at about 13 degrees; as the outer bees cool down, they push inward and warmer ones move to the outside. Two things follow from this for the apiary: in summer the hive must not stand in blazing sun and the entrance must not be too narrow; in winter it is not the cold that causes harm, but damp and draft.