Influence of group size and composition on soldier differentiation in female final larval instars of a higher termite, Macrotermes michaelseni

. Experiments with Macrotermes michaelseni (Sjöstedt), involving artificial groups of different sizes of final larval instar females, showed that the proportion of presoldiers produced in each group decreased exponentially with increase in the size of the colonies. This relationship was not smooth, however, but stepwise. Increasing the number of workers in a group with larvae improved the chance of the larvae differentiating into presoldiers, although the normal proportion of soldiers for the species was not achieved under these conditions, even at maximum crowding. The inhibitory effect of soldiers in stopping larvae differentiating into more soldiers was established, and evidence obtained for a non‐volatile or low volatility pheromone. It is postulated that dominance by larvae which have acquired ‘competence’ over others, allows them to suppress these others from differentiating into presoldiers through the pheromone acting on specific behavioural elements.