Organization of work via a natural substance: regulation of nest construction in social wasps.

In social insects, colony-level complexity emerges from simple individual-level behaviors and interactions. In the evolution of insect societies, selection has acted to promote efficiency through division of labor. Nest construction of social wasps is an excellent model system to study division of labor and the performance of a decentralized behavioral regulation. After re-examination of Jeanne's (1996) demand-driven "non-taskmates feedback" hypothesis, an alternative mechanism is suggested whereby the regulation of behavior is based on a natural substance (water) which is itself also a building material. By experimenting with a simple model system, we show that the model's predictions agree with observational data and cover a wide range of evolutionary transitions. According to the internal and external parameters, the colony builds up storage of water that is used both as regulator and building material. Through individual interactions, pulp foragers and water foragers emerge from general laborers and their ratio becomes balanced. The emergent foragers ensure both the stabilization of the quantity of stored water and the steady construction of the nest according to the given conditions. Perturbations of the system alter colony-level dynamics in a similar way as was observed in nature: water and pulp addition increase pulp arrivals and building rate; removal of pulp foragers decreases pulp input and construction rate, but not the water influx; removal of water foragers causes overcompensation of water input after a delay. After comparing the predictions of the model to natural data, assumptions found in the literature on organization of work and regulation of behavior are re-examined. A new, more parsimonious model of organization of work is proposed that may cover wide variety of cases where hormones and learning cannot be accounted for the regulation of behavior.