Hexagonal comb cells of honeybees are not produced via a liquid equilibrium process
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ORIGINAL PAPER
Hexagonal comb cells of honeybees are not produced via a liquid equilibrium process Daniel Bauer & Kaspar Bienefeld
Received: 10 August 2012 / Revised: 2 November 2012 / Accepted: 3 November 2012 / Published online: 14 November 2012 # Springer-Verlag Berlin Heidelberg 2012
Abstract The nests of European honeybees (Apis mellifera) are organised into wax combs that contain many cells with a hexagonal structure. Many previous studies on combbuilding 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. Keywords Cell geometry . Comb building . Honeybee comb . Liquid equilibrium hypothesis
Introduction The nests of honeybees are organised into parallel, vertical aligned wax combs made of self-synthesised wax. Both sides Communicated by: Sven Thatje Electronic supplementary material The online version of this article (doi:10.1007/s00114-012-0992-3) contains supplementary material, which is available to authorized users. D. Bauer : K. Bienefeld (*) Institute for Bee Research Hohen Neuendorf, Friedrich-Engels-Str. 32, 16540 Hohen Neuendorf, Germany e-mail: [email protected]
of the comb are comprised of arrays of horizontal standing, hexagonal cells that are used as spaces to house the brood and to store resources. In the perfect hexagonal cell, the six walls have the same size and adjoin at a 120° angle. The bottom has a pyramidal form consisting of three rhomboid plates (Werner-Meyer 1960). Because neighbouring cells share one common cell wall or one common bottom plate, the cells are perfectly interlocked and the work at one cell wall or bottom plate influences the geometry of two cells (Fig. 1). So the geometry and the organisation of the cells appear to provide the best compromise for space utilisation and stability. The sizes of cells can differ among honeybee races. The average worker cell produced by Apis mellifera carnica is 5.3 mm in width between two parallel cell walls and 10– 12 mm in depth, while the drone cells have an average width of 6.9 mm and a depth of 14 mm. Apart from a few details, there has been no previous demonstrations of how honeybees generate the specific geometrical structures of their cells (Martin and Lindauer 1966; Hepburn 1
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