Interspecific competition between Solenopsis invicta Buren and eight other ant species

Solenopsis invicta Buren is one of the most important invasive pests in China and competes aggressively with native ants. This study investigated competitive interactions between eight ant species and S. invicta , and the defensive chemicals involved, using individual and group competition tests and toxicity bioassays. Results showed that Tapinoma melanocephalum exhibited the lowest attack frequency against S. invicta in individual contests, while Pheidole megacephala caused low mortality in group trials. Camponotus japonicus showed the highest level IV attack intensity and caused the highest mortality, followed by Oecophylla smaragdina . Camponotus nicobarensis and Camponotus pseudoirritans achieved the highest mortality at a 1:1 ratio. Mortality caused by Polyrhachis dives and Anoplolepis gracilipes decreased with increasing numbers of S. invicta . Blocking acid gland pores significantly reduced mortality by these dominant species. Toxicity tests indicated that hexadecane had the strongest fumigation toxicity, while hexadecane and nonadecane showed the highest contact toxicity. These findings suggest that several native ant species can competitively suppress S. invicta , and their defensive pheromones play a key role. Utilizing such native ants could contribute to integrated management of S. invicta .