The Social Organisation of <em>Oecophylla smaragdina</em> (Hymenoptera: Formicidae) Colonies and Their Functional Activity

Abstract

The Asian weaver ant Oecophylla smaragdina is a natural enemy (predator) used as a biological control agent in Australia and several Southeast Asian nations against the most destructive and economically important oriental fruit fly Bactrocera dorsalis. For biological control of the invasive bagworm species Metisa plana in oil palm plantations, the composition of the colony's social structure was investigated to ensure its efficacy. On two colonies, all castes were examined stereo microscopically after nest collection and dissection. The head's width, head, thorax, abdomen, and body lengths of workers were evaluated during the morphology analysis. All colonies with more than a thousand eggs comprise of a founding egg-laying queen, reproductive winged green and newly emerged yellow queens, as well as adult drone males and workers. Future queens, males, and workers' pupae and larvae comprised immature individuals. It is the first study to characterise one caste of minor workers, two previously unidentified castes of intermediate workers, and two castes of major workers. The lengths of the body and abdomen are proposed as differentiating factors for workers. The discovery of a polymorphic size frequency distribution model contrasts with the consistently reported existence of archetypical bimodal systems in ants. Intermediate workers foraging outside the nest revealed reconnaissance and aggressive behaviours that aided major workers in their daily tasks. Due to their short lifespan and segregated nests, it is difficult to successfully sample adult males in wide plantations. An entire year's worth of reproductive individuals are produced by stable, three-year-old colonies, with a decrease in population size correlated with a significant decline in rainfall interception.