Nuptial flight of the Southeast Asian plant-ant Crematogaster captiosa (Forel, 1911) and the phenology of colony founding

Despite the great importance of nuptial flights for ants, little is known about the swarming processes from the highly diverse tropical regions, especially rainforests. This is particularly true for ants living in obligate symbiosis with myrmecophytic plants. Here we present the first direct observations of the swarming event in the association between Crematogaster captiosa and the pioneer tree Macaranga bancana in Southeast Asia. Nuptial flights of C. captiosa on M. bancana took place during the night, and alate females were seen to copulate with alate males on the tree. Data on C. captiosa from the Malay Peninsula as well as Borneo indicate that sexual production and colony founding occurs throughout the year. Despite episodic fruiting seasons of the host plants, Macaranga saplings for colony founding can also become available outside peak seasons from seed banks after disturbance. Therefore, continuous swarming might be a good strategy to avoid strong competition for limited nesting sites while still securing permanent colonisation of saplings - a prerequisite for their survival.