Imperfect comb construction reveals the architectural abilities of honeybees

Abstract

Honeybees are renowned for their perfectly hexagonal honeycomb, hailed as the pinnacle of biological architecture for its ability to maximize storage area while minimizing building material. However, in natural nests, workers must regularly transition between different cell sizes, merge inconsistent combs, and optimize construction in constrained geometries. These spatial obstacles pose challenges to workers building perfect hexagons, but it is unknown to what extent workers act as architects versus simple automatons during these irregular building scenarios. Using automated image analysis to extract the irregularities in natural comb building, we show that some building configurations are more difficult for the bees than others, and that workers overcome these challenges using a combination of building techniques, such as: intermediate-sized cells, regular motifs of irregular shapes, and gradual modifications of cell tilt. Remarkably, by anticipating these building challenges, workers achieve high-quality merges using limited local sensing, on par with analytical models that require global optimization. Unlike automatons building perfectly replicated hexagons, these building irregularities showcase the active role that workers take in shaping their nest and the true architectural abilities of honeybees.

Stigmergy versus behavioral flexibility and planning in honeybee comb construction

“…An interface between worker and drone cells can result from a transition or a merger of two construction sites, both of which introduce irregular cells with variations in both area and wall length. The analysis ( 2 ) shows a distinction between the controlled transition between worker and drone combs, compared with the less-coordinated merger between two tongues of downward-growing comb. In the former case, the cells within the interface were found to change progressively from one size to the other and resulted in few that were too small, while merge zones contained a wider spread of size with many less usable, smaller cells.…”

“…This typically highly regular structure has been shown to be mathematically optimal to maximize storage space and stability while minimizing building material ( 1 ). However, Smith et al ( 2 ) show that bees also build various types of irregularly shaped and sized cells, for example when merging separate comb constructions. This raises the question of whether the bees’ innate behavioral repertoire contains multiple different routines for each shape, whether bees plan ahead to insert optimal shapes, or whether such diversity of structures could be explained by simple rules.…”

“…As they are extended, they come into contact so the bees must adapt the cell structures to merge those of differing size, orientation, and offset. Smith et al ( 2 ) explore how bees cope with these many challenges and ask whether comb-constructing bees can be regarded as automatons or architects.…”

“…Smith et al ( 2 ) show that adaptations between areas of cells of differing tilt requires smaller adjustments where the cells are more closely aligned, hence a progressive change of tilt to match one with another should result in reduced irregularity and fewer nonhexagonal cells. While there is a greater variation of both wall length and the number of walls per cell within an interface zone, the distribution remains bimodal, aligning well with the values typical of either drone or worker cells ( 2 ). The most common nonhexagonal cells (pentagons and heptagons) were often found in pairs or triplets, where a cell with a surplus face was found adjacent to with another with fewer.…”

“…It would appear, therefore, that bees have a repertoire of techniques which by default will build regular cells of a set size yet can also build regular cells of a different size, graduate from one size to the other, merge mismatched cells, cope with irregular foundation, and generate curved architecture through lateral asymmetry ( 9 , 10 ). Furthermore, it appears that the technique chosen for a particular adaptation is well-suited to the task as few cells are produced that are distorted to the point of being unusable ( 2 ). Cells that are of an incorrect size or not hexagonal will seldom be used to raise brood but will be utilized for food storage and so are not wasted.…”