Birds and mammals create nests that are not much bigger than themselves, but the nests built by social insects, such as termites, are anything but cramped. In fact, a termite nesting-mound is so large that no single termite can perceive the full scope of a mound’s size. A termite mound is several million times larger than an individual termite, and mounds can take several generations to complete. For termites, the mound is like a world of its own, and even humans cannot help but to marvel at the enormity of some mounds, which can reach 30 feet in height. In addition to being large, termite mounds are also architecturally complicated, as a mound’s structure must include features that allow for internal temperature control. These features include thermoregulatory veins, air conditioning vents and sometimes a chimney system. Considering the complicated structure of termite mounds, experts used to believe that one single termite, likely the queen, was responsible for directing worker termites on how to construct an entire mound. Although the queen’s pheromones do prompt termite workers into building the first stages of a mound, termite workers complete termite mounds by means of a process known as self-organization.
The idea of the queen as a sort of foreman that coordinates mound construction was scrapped once researchers realized that one queen could not possibly communicate with the many thousands of individual worker termites within a colony. Mound construction is also not facilitated by communication between termite workers; instead, termite workers are directed by the structure itself. Termite workers rely on environmental information to direct their actions during construction. Altering the structure (environment) of a mound in progress will alter the environmental information received by a termite, which therefore, alters the building behavior of termites. This helps explain why termites are quick to repair even trivial damages to a mound immediately when damages occur. This method of communication that is prompted by alterations in the environment as opposed to direct communication between agents (worker termites) is known as stigmergic behavior. Mound-building termite workers demonstrate stigmergic behavior by adding materials onto a mound, and this addition of new building materials will prompt another worker to behave accordingly after seeing the new addition. While the queen’s royal chamber is constructed via pheromone messaging from the queen to worker termites, stigmergic communication plays a much bigger role in mound construction.
Can you think of any other social insects that rely on stigmergic communication during nest construction?