Interface accommodation of asymmetric cells in the Apis mellifera honeycomb

Honeycomb is an engineering and architectural marvel used by bees to store food and raise brood. It is constantly being added to or subtracted from by workers in the colony. The size and shape of comb can vary dramatically based on need, and workers often have to merge or manipulate comb of varying size and shape. This variation in cell sizes causes the bees to adjust construction of the hexagonal comb lattice to accommodate the inherent distortions caused by size differences. Here, we shed light on lattice distortions at the interface between worker (small) and drone (large) cells, as well as around non-polygonal queen cells. Using time-resolved X-ray microscopy, we show that the merger between two combs is initially facilitated by the copings- a bulb like structure that extends the corrugated spine of the comb. We show that bees attempt to maintain the corrugated nature of the spine in the merging region and inevitably end up creating distorted cells that they later attempt to normalize. To highlight this, we propose a new distortion parameter to quantify in 3D, distortions within cells and thereby quantifiably show how bees modify individual cells to lower this parameter to a proposed threshold level. Finally, we shed light on a previously overlooked interface between a typical honeycomb lattice and non-polygonal queen cells and describe how bees use a previously unreported strategy of building interstitial cells to incorporate highly irregular cells into the ordered hexagonal lattice of the comb. STATEMENT OF SIGNIFICANCE: It has been speculated for years that honeybees have developed efficient design principles and valuable strategies to optimally use materials and resources when constructing comb. Studying and understanding these complex structures, non-destructively as the bees build them out, can be challenging. In our paper, we have used four-dimensional x-ray microscopy, to unravel several unique and previously unreported mechanisms for interface accommodation between different honeycomb cells. Here we show, at a microscopic level, that the coping at the edges of the comb is used to link and accommodate the cells of different sizes. More importantly, we have developed a quantitative methodology to capture the deviation in shape of the hexagonal cell to capture the degree of accommodation at the interface.