Figure 3. Average aggression scores of ants.

Average aggression of (A) Argentine ants towards M. antarcticum, O. glaber and T. jocosus and (B) M. antarcticum, O. glaber and T. jocosus towards Argentine ants depending on the treatment with different concentrations of synthetic trail pheromone (Z)-9-hexadecanal (measured in µg pheromone per µl solvent). Aggression was scored as 0 = no interest or aggression; 1 = interest shown via antennation; 2 = ant retreats quickly; 3 = lunging, biting or leg-pulling, rising of gaster and exuding venom; 4 = prolonged (>5 s) incidences of aggression, individuals locked together and fighting. Error bars represent Standard Error of average aggression scores.