Distribution of haemolymph in the honeybee (Apis mellifica) in relation to season,age and temperature

¹⁴C]Polyethylene glycol was proved to be a suitable marker for the determination of the extracellular space, which is identical with the volume of the haemolymph in insects. Bees kept at temperatures above 22°C show a fast circulation of haemolymph independent of the season. In winter at 5–25°C, immobilized isolated bees have a thoracic temperature which differs very little from that of the ambient. Under these conditions the time of mixing and the amount of haemolymph in head, thorax and abdomen depends on the temperature. At 5°C bees have much more haemolymph in their heads than at 25°C. At low temperatures the mixing time was increased and finally the mixing process was nearly stopped. Although bees are motionless at 5°C, limited activity of the circulatory system could be shown.The correlation between these distribution studies and the functional status of the bees within their colony is discussed.