The wax-made comb of the honeybee is a masterpiece of animal architecture. The highly regular, double-sided hexagonal structure is a near-optimal solution to storing food and housing larvae, economizing on building materials and space. Elaborate though they may seem, such animal constructions are often viewed as the result of ‘just instinct,’ governed by inflexible, pre-programmed, innate behavior routines. An inspection of the literature on honeybee comb construction, however, reveals a different picture. Workers have to learn, at least in part, certain elements of the technique, and there is considerable flexibility in terms of how the shape of the comb and its gradual manufacture is tailored to the circumstances, especially the available space. Moreover, we explore the 2-century old and now largely forgotten work by François Huber, where glass screens were placed between an expanding comb construction and the intended target wall. Bees took corrective action before reaching the glass obstacle, and altered the ongoing construction so as to reach the nearest wooden wall. Though further experiments will be necessary, these results suggest a form of spatial planning skills. We discuss these findings in the context of what is now known about insect cognition, and ask if it is possible that the production of hexagonal wax combs is the result of behavioral heuristics where a complex structure emerges as the result of simple behavioral rules applied by each individual, or whether prospective cognition might be involved.

Honeybee comb comprises recognisable hexagons, each with straight sides. Not only are the cell side-walls flat, but so too are those that form the base of cells; base faces which are shared with cells on the opposite face of the comb. The mechanism by which bees build cells with flat sides has been the subject of speculation for centuries, but it has been conjectured by Kepler, Darwin as well as more recent researchers that bees build cylindrical cells that are transformed into flat sided prisms, without consensus as to the process by which this is achieved. By offering bees shaped wax stimuli and observing the comb that was built upon them, we have shown that under certain conditions walls will be curved and others where walls are reformed to be flat. A wall of a cell, be it a side-wall or a face of the base, with no other cell beyond it will be built as a convex curve whereas a wall with a cell to both sides will be formed flat. Furthermore, we show that these walls are plastic; walls that were initially built curved were re-shaped to be flat once a second adjacent cell had been built.

The comb of honeybees has long been admired for its even hexagonal layout, but such a regular geometry is possible only if it comprises isodiametric cells arranged in a regular pattern of one surrounded by six others. The support structure of a natural nest will not provide a horizontal smooth surface and so will force irregularities, as will the merging of individual tongues of comb, introduction of accidental errors or the inclusion of larger drone cells. These perturbations force within regular comb the construction of non-equilateral or non-equiangular cells, or those that are non-hexagonal. Using automated image analysis, we extracted cell geometry from naturally built comb and that built on wax stimuli at different stages during comb construction. We show that, when faced with disruption, the bees initially build cells that are uneven and irregular, but that following further construction effort they bees reform those cells. The eventual comb exhibited increased homogeneity of cell area; cells that were more equilateral and equiangular. Overall regularity, or progressive transition of cells from one size or alignment to another arose through adjustments to each cell after the initial steps of comb construction.

Honeybee comb architecture and the manner of its construction have long been the subject of scientific curiosity. Comb is characterised by an even hexagonal layout and the sharing of cell bases and side walls, which provides maximised storage volume while requiring minimal wax. The efficiency of this structure relies on a regular layout and the correct positioning of cells relative to each other, with each new cell placed at the junction of two previously constructed cells. This task is complicated by the incomplete nature of cells at the edge of comb, where new cells are to be built. We presented bees with wax stimuli comprising shallow depressions and protuberances in simulation of features found within partially formed comb, and demonstrated that construction work by honeybee builders was influenced by these stimuli. The building of new cells was aligned to concave stimuli that simulated the clefts that naturally appear between two partially formed cells, revealing how new cells may be aligned to ensure proper tessellation within comb. We also found that bees built cell walls in response to edges formed by our stimuli, suggesting that cell and wall construction was specifically directed towards the locations necessary for continuation of hexagonal comb.

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