Figure 2.

Relationship between degree of intraspecific aggression and distance between nest pairs at each of 15 sites within native (A) and introduced (B) ranges of the Argentine ant. Native populations typically exhibited pronounced intraspecific aggression over short distances. In contrast, intraspecific aggression was rare in introduced populations. Aggression between nests was measured by using a behavioral assay ranging from 1 (no aggression) to 4 (high aggression).