The significance of social interactions in synchronized swarming flight in a termite

Abstract

In social insect colonies, individuals of working caste coordinate their actions to manage various collective tasks. Such collective behaviors are observed not only in working castes but also in reproductives. During certain seasons, newly emerged winged reproductives (alates) fly from the nest to disperse and find mating partners in a synchronized manner. Although this "swarming" behavior is one of the collective behaviors that involve the greatest number of individuals in social insects, underlying social interactions remain unexplored. Here, we show that synchronized flight among colony members results from collective decision-making. Our simple simulation model suggests that social interactions in a large group of alates enable synchronized flight within a nest under fluctuating environmental conditions. This model is supported by empirical experiments using a termite Reticulitermes kanmonensis. Under the semi-field environment with fluctuating temperatures, alates within the same colony synchronized their dispersal flight under higher air temperatures, while dispersal flight was suppressed under lower temperatures. Furthermore, termites could synchronize their dispersal flights even under laboratory conditions with constant temperature, indicating that environmental cues are not always necessary for synchronization. In either case, higher synchronization happened with a larger number of alates. All these results demonstrate that both environmental and social factors interplay to enable the synchronized swarming flight of social insects.