Hexagonal comb cells of honeybees are not produced via a liquid equilibrium process
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The nests of European honeybees (Apis mellifera) are organised into wax combs that contain many cells with a hexagonal structure. Many previous studies on comb-building behaviour have been made in order to understand how bees produce this geometrical structure; however, it still remains a mystery. Direct construction of hexagons by bees was suggested previously, while a recent hypothesis postulated the self-organised construction of hexagonal comb cell arrays; however, infrared and thermographic video observations of comb building in the present study failed to support the self-organisation hypothesis because bees were shown to be engaged in direct construction. Bees used their antennae, mandibles and legs in a regular sequence to manipulate the wax, while some bees supported their work by actively warming the wax. During the construction of hexagonal cells, the wax temperature was between 33.6 and 37.6 °C. This is well below 40 °C, i.e. the temperature at which wax is assumed to exist in the liquid equilibrium that is essential for self-organised building.
KeywordsCell geometry Comb building Honeybee comb Liquid equilibrium hypothesis
We thank Uwe Gerber for the support with constructing the observation unit. We also thank two anonymous referees for their valuable comments. This work was supported by funds from the regional governments of Brandenburg, Berlin, Saxony, Saxony-Anhalt and Thuringia. Part of the equipment used was financed by the European Union (EFRE–Application No. 80137041).
Cross section of a comb containing building bees. In this infrared video, the building technique of single bees is shown inside and above the cells (AVI 22777 kb)
Thermographic view of comb building. This video shows the comb building behaviour in a thermographic view. The colour scale provides information about the temperature. A cell was excised in each of windows 1 and 2, and builders performed repair work. The area with warm bees below is the comb edge (AVI 11752 kb)
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