Knowledge Bank

The well-studied Megalomyrmex ant parasites are known for their use of venom alkaloids to reduce aggression and confuse their fungus-growing ant hosts. However, most Megalomyrmex species are not restricted to a parasitic lifestyle. In fact, many are free-living ants that compete with other ant species by foraging from insect carcasses and other food sources on the rainforest floor, one such example being Megalomyrmex peetersi. Another ant, Aphaenogaster araneoides, is a sympatric species that is often the first to arrive at a food source. Our field observations suggest that, despite arriving later, M. peetersi dominate baits and cause A. araneoides to flee. Megalomyrmex peetersi appears to use venom to behaviorally manipulate and outcompete other ant species to gain control of food resources. To test this hypothesis, we exposed foraging Aphaenogaster workers to M. peetersi venom extracts at two field locations (one with M. peetersi presence [n=26], and one without [n=26]) . We controlled for the venom extract’s solvent and the act of applying the stimuli. Behaviors were video recorded and scored using BORIS software. We predicted that M. peetersi venom exposure will cause A. araneoides foragers to react submissively (i.e., repulsion, recoil, or flight) compared to the controls. We did not find support for our hypothesis, but a trend that suggests A. araneoides react more submissively when exposed to M. peetersi venom. We also found that the presence of food significantly increased the latency of submissive A. araneoides reactions. This work suggests that venom may not be the only mechanism used by M. peetersi to dominate a food source when competing with A. araneoides, and that the lack of support for our hypothesis may be influenced by A. araneoides' sensitivity to overhead motion. This suggests that studies that account for visual stimuli are needed, as multiple stimuli likely influence A. araneoides' behavior. These additional field studies will enhance our understanding of the complex dynamics that surround resource competition and venom use between these ant species.