Group Decision Making in Nest-Site Selection Among Social Insects

The choice of a new nest site is ecologically critical for an insect colony. In swarm-founding social insects, or those that move as colonies from one site to another, this choice is one of the best-available examples of a distributed, nonhierarchical decision-making process in animals. In the few species of ants and bees that have been studied in detail, the main features of this collective decision making are strikingly similar, although some differences occur. Individual scouts discover potential nest sites and integrate multiple properties of these sites into assessments of their quality. The discovered sites then compete for a limited pool of nest-site scouts, and attrition of less-favored sites occurs by several mechanisms. Finally, the mass movement of the colony to the new site is triggered by a quorum-sensing mechanism when sufficient scouts are present at one of the alternatives. Movement itself is coordinated by different mechanisms in different insects.