Latency time and absence of group effect

Abstract

Summary We suggest that group effect need not be invoked to explain the differences in latency times exhibited by groups of different sizes in the initiation of building in the termite Macrotermes subhyalinus (Rambur). A simple, alternative, model is presented, that is fully consistent with experimental data. In a remarkable series of laboratory experiments Bruinsma (1979) studied the building behavior of the fungus-growing termite Macrotermes subhyalinus, in particular the construction of the royal chamber in the presence of a live physogastric queen. Among his observations is the fact that the time it takes for a group of termites to initiate the building of the royal chamber (which, following Bruinsma, we shall call building “latency time”) is a nonlinearly decreasing function of groups size. Such an observation could be interpreted as resulting from a group effect (Grasse, 1946), or socially facilitated behavior (Clayton, 1978). However, a simple model that does not invoke group effect, fully consistent with the data of Bruinsma (1979), can very satisfactorily account for this observation. The behavior of individual workers during building seems to be made up of relatively few and relatively simple activities: a worker picks up a piece of soil close to or underneath the queen, transports the pellet to a site of deposition (a narrow band around the queen at 2‐5 cm from her and determined by a pheromonal template that she emits), where it deposits and cement it. This behavior, combined with an attraction towards sites where pellets have already been deposited, leads to the formation of pillars or columns a few centimeters away from the queen. Pillars are lengthened until they reach a height of between 0.5‐0.8 cm; workers then start to build horizontal lamellae that grow from the pillars to form a roof over the queen; finally, the interpillar space is filled with pellets to form walls. The building latency time, that is, more precisely, the time elapsed between the introduction of workers in the arena with