Termites: Nest Building

System Behavior: Tropical termites construct mounds that can exceed five meters in height and ten tons in mass, without central control.
Responsibilities:
1. Metabolize bodily waste, which contains pheromones. The mounds are constructed from this material
2. Wander randomly, preferring the strongest pheromone concentration.
3. At each time step, decide stochastically whether to deposit the current load of waste. The probability increases with pheromone intensity and the amount of waste the termite is carrying.
Integration: Initial deposits will tend to attract termites and become bigger. Because pheromones decay and aggregate, the most recent deposits at the center of the pile are the strongest, so a tower is built.