Aggressive interactions between Solenopsis geminata and Paratrechina longicornis (Hymenoptera: Formicidae)

Solenopsis geminata introduced into central and southern Taiwan over thirty years. In this study, ant species were investigated using pitfall traps and bait traps in the fire ants infested sites in Taichung (central Taiwan). Results from the pitfall traps showed that Paratrechina longicornis was more common in the infested areas. In bait traps, P. longicornis was faster in finding food. Conversely, S. geminata was considerably faster in recruiting and occupying food. We conducted a series of inter- and intra-specific behavioral assays to examine the aggressive response of S. geminata and P. longicornis, using individual and group assays. In interspecific individual aggressive interaction, S. geminata always exhibited significantly more aggressive than P. longicornis. The results showed that while S. geminata played resident or intruder role, the mortality in 24 hours after interaction was 66.7% or 64.4%, respectively. On the other hand, the mortality while P. longicornis played resident or intruder role was 84.4% or 77.8%, respectively. In group assays, the mortality of S. geminata and P. longicornis were 44% and 94%, respectively. The result of the study provides a preliminary understanding which S. geminata and P. longicornis inhabited in the same area as well as the strategies they used to compete the same resource and habitat. S. geminata is more aggressive and quick in recruiting; P. longicornis, on the contrary, is in evasive manner. Using baiting and interspecific aggressive interaction experiments helps to understand the role S. geminata plays in the ecosystem and its influence to other ant species.

Key words: Solenopsis geminata, Paratrechina longicornis, pitfall traps, bait traps, aggressive interactions