Figure 1.

Foundresses' behavioural responses towards the presentation of stimuli with different amounts of a total foreign foundress' CHC quantity. Foundresses (N = 22) increase their responses according to the increase in CHC amount. Time spent in the behavioural responses differs between the treatments. The full concentration elicited significantly stronger responses than the one-third concentration. The one-third extract did not elicit more aggressive responses than the control, while the two-third and the full amount extracts did. Box plots represent the medians (thick horizontal lines), the interquartile range (boxes), the top and lowest quartiles (horizontal lines) and the outliers (circles).