Little sons and big daughters: Honeybee queen cell size experience effects on egg laying behaviour

The ability to internally measure space and the consistency of such measurements has long been of interest in the study of animal behaviour– honey bees (Apis mellifera) may exhibit the pinnacle of such abilities as seen in their precise comb construction behaviour. Honey bee queens also have the unique ability to determine the sex of their offspring, a decision that is largely influenced by the cell size of the brood comb. The queen measures the cell size with her tarsi and typically lays fertilized, female-destined eggs into cells of approximately 5 mm in diameter and unfertilized, male-destined eggs into drone cells of approximately 6.5 mm in diameter. Additionally, queen-destined female eggs have been found to be larger than worker-destined female eggs. Natural colonies are also known to exhibit considerable variation in acceptable cell sizes, leading to the question of whether a queen’s oviposition behaviour differs based on cell size. In this study I look at the size differences of eggs laid in differently sized cells. Queens were presented with a gradient of 3D printed cells ranging from 3.46 to 8.05 mm in diameter - a range that includes cells both much smaller and much larger than have been previously tested with honey bees. Two groups of queens were tested, one early in the honey production season and one late. Eggs were grafted out of the cells, photographed, and measured. Resulting egg size and oviposition patterns on the variable comb were then examined. Egg size was found vary significantly depending on cell size, with larger eggs being laid at both extremes. This study demonstrates that egg size is a dynamic trait that queens can adjust, with potential implications for colony structure.