Role of extrafloral nectaries of Vicia faba in attraction of ants and herbivore exclusion by ants

We directly evaluated the role of extrafloral nectaries (EFN) in ant attraction and herbivore exclusion by experimental removal of EFN in the laboratory. When EFN of Vicia faba Linnaeus (Leguminosae) were artificially removed, the number of workers of Tetramorium tsushimae Emery (Hymenoptera: Formicidae) visiting the plant decreased, and the efficiency of herbivore exclusion by ants also decreased. Herbivore exclusion by ants was mostly ineffective on a plant when less than four workers visited the plant, but when more than four workers visited, the time a herbivore resided on the plant decreased rapidly with increasing numbers of visiting ants. Therefore, the efficiency of herbivore exclusion from a plant is determined by the number of ants visiting, and EFN play an important role in ant attraction.