Competitive Interactions Between the Yellow Crazy Ant and the Red Imported Fire Ant (Hymenoptera: Formicidae)

The red imported fire ant, Solenopsis invicta Buren, was first detected in southern mainland China in 2005. The yellow crazy ant, Anoplolepis gracilipes (F. Smith), also occurs in southern China. We studied the interspecific interaction of these 2 invasive pest ants at food resources. Our observations showed that A. gracilipes workers were more aggressive than S. invicta workers when competing for cricket baits. Anoplolepis gracilipes successfully excluded S. invicta at almost 90% of the cricket baits at which the 2 species occurred simultaneously by attacking, killing, or successfully repelling foraging S. invicta workers. Such competitive interactions did not occur at baits composed of ham, thus suggesting that A. gracilipes would be a potent competitor with S. invicta when the food preferences of the 2 species overlap.