Pogonomyrmex Mayr harvester ants (Hymenoptera:Formicidae): an additional cost associated with dung beetle, Canthon imitator Brown (Coleoptera: Scarabaeidae), reproduction?

Harvester ants, Pogonomyrmex barbatus (F. Smith), exerted an energetic cost on the dung beetle Canthon imitator Brown through behavioural interference, by causing brood ball abandonment. This was verified experimentally in eight independent trials. Significantly more C. imitator (87.5%) abandoned brood balls after encountering P. barbatus on ant mounds. No fatalities were recorded from trials although harvester ants were observed to sting and bite dung beetles. Five transects revealed a mean of 10.8±1.11 (range: 9-15) ant mounds/200 m. For a total of 54 ant mounds, brood balls occured at a mean of 1.3±0.31 (range: 0-13)/mound. Compared to random points, brood balls occured significantly more often on ant mounds (48% of mounds contained brood balls).