Behavioural evolution and domestic degeneration in obligatory slave-making ants (Hymenoptera: Formicidae: Leptothoracini)

The foraging and nest emigration abilities of the obligatory slave-making ants, Harpagoxenus canadensis, H. sublaevis and H. americanus, were examined in laboratory experiments involving both natural and slave-deprived colonies. The slave-makers contributed relatively little to these domestic tasks when slaves were present, but their apparent abilities expanded to varying degrees in the absence of slaves. H. canadensis appeared to be the most self-sufficient of the three species and displayed a surprisingly full repertoire of foraging and emigration behaviour, including the ability to recruit nestmates by ‘tandem running’ in both contexts. The relative degree of domestic degeneration in these species was correlated with the extent of their behavioural specialization for conducting slave-raids. These results reinforce current views regarding the evolution of slavery among leptothoracine ants.