A field study was conducted to determine if Argentine ants would be attracted from a nest entrance and nearby trails to an aqueous pheromone spray deposit. The red circles indicate the positions of ants. The sand patch on right was sprayed with water supplemented with the synthetic pheromone (Z)-9-hexadecenal. The sand patch on left was sprayed with water only. After a few minutes, the number of ants on the pheromone-treated patch exceeded the number of ants on the water-treated patch. The nest entrance and nearby trails were located between the patches of sand.