Meeting Abstract
Social insects maintain order despite large and varying number of group members and changing environmental conditions. For instance, in termite mounds, the numbers of individuals can fluctuate a great deal, as do the ambient conditions under which they operate in their underground nests. Previously, we showed that when a mound surface is breached, the termites (Odontotermes obesus) can repair the breach within a short duration through their collective actions. This observation suggested that there is an increased traffic towards the breach. How well-ordered is this collective movement within the nests? In general, how do termites modulate their traffic towards a breach in the mound? To address these questions, we developed a laboratory assay to study collective movement of termites. Termites were introduced in a circular arena, and their milling behaviour monitored while altering the ambient conditions within the arena. Our experiments show that whereas mechanosensory cues are required to initiate the milling behaviour, after some duration the termites lay pheromone trails that provide chemical cues to help maintain other members on a trail. This behaviour is density-dependent such that greater number of termites within the arena means that behaviour is initiated earlier. We have also conducted experiments to monitor such movements in natural conditions by introducing a camera deep within the mound through a breach. We observed termites moving in small groups towards the breach through tunnels, and forming transient lanes as they moved towards the breach, and their number increased with time. Together, these results show that termite movement in both laboratory and nature is highly ordered, and maintained by mechanical and chemical cues.
