Colony Fissioning In Honey Bees: How Is Swarm Departure Triggered And What Determines Who Leaves?
Honey bees (Apis mellifera) live in colonies that reproduce by fissioning. When a colony divides itself, approximately two thirds of the workers along with the (old) mother queen, leave the hive as a swarm to found a new colony else where. The rest of the workers, and a (new) daughter queen, stay behind and inherit the old nest. In cold, temperate regions, this ephemeral process of colony multiplication typically occurs only once per year and takes less than 20 minutes, making it a hard-to-study phenomenon. The purpose of this dissertation, which is divided into four chapters, was to uncover the mechanisms and functional organization of the colony fissioning process in honey bees. The first chapter explored the signals used by honey bee colonies to initiate the departure of a swarm from its nest, finding that the piping signal, and the buzz-run signal, are the key signals used to initiate the swarm’s departure. The second chapter searched for the identity of the individuals that performed the signals that trigger the swarm’s exodus. We now know that knowledgeable nest-site scouts are the producers of the signals that trigger this sudden departure. The third chapter investigated whether honey bee swarms compete for, and defend, potential nest sites during their house-hunting process. We found that they do so, using various levels of aggression depending on the number of nest-site scouts from each swarm present at the nest site at the same time. The fourth and final chapter looked at the question of whether honey bee workers make a decision of whether to stay in the old nest, or leave with the swarm, based on their genetic relatedness to the queen(s) that inherit the nest during colony fissioning. Our findings showed that there is no intracolonial nepotism during swarming, despite the theoretical prediction that workers should benefit from preferentially staying in the old nest based on their genetic relatedness to the daughter queen(s). These studies have helped us better understand important aspects of the reproductive biology of honey bees, and now serve as the basis for future research regarding colony fissioning in honey bees and other social insects.
dissertation or thesis