Average aggression scores of ants.

<p>Average aggression of (A) Argentine ants towards <i>M. antarcticum</i>, <i>O. glaber</i> and <i>T. jocosus</i> and (B) <i>M. antarcticum</i>, <i>O. glaber</i> and <i>T. jocosus</i> 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.