Modelling the Role of Trail Pheromone in the Collective Construction of Termite Royal Chambers

Experiments with worker termites constructing a royal chamber around a termite queen in species Macrotermes subhyalinus (Rambur) have shown that both trail and cement pheromones are involved and necessary for the successful formation of pillars during the building process. However, earlier models of the construction were able to demonstrate stigmergic pillar formation with cement pheromone alone. We present results from a new three-dimensional agent-based model, developed to investigate the role of trail pheromone in the construction process. The model is able to demonstrate how, if the properties of the cement pheromone are altered so that its attractive influence is more localised than in earlier models, termites are unable to produce significant pillar formation. The model shows how the addition of trail deposition and following effectively increases the range of the stigmergic effect so that pillar formation is restored. The presence of trail pheromone also results in pillars which are narrower than those produced by cement pheromone alone, and which show more pronounced lateral extensions. Additionally the paths that the termites take from the termite queen to building sites become more directed with time. These features are in keeping with observation and have not been previously modelled.