Cuckoos and parasitic ants: Interspecific brood parasitism as an evolutionary arms race.

Each summer thousands of nesting birds feed cuckoo chicks that have killed the hosts' own young. Likewise, worker ants rear the brood of other ants that have killed the workers' queen or even induced the workers to kill their queen themselves. In both cases the hosts spend time and energy raising offspring that, to them, are of no genetic value. Such exploitation involves intricate parasitic adaptations for deceiving hosts. It should also provoke host defences. Brood and social parasites and their hosts therefore provide excellent opportunities for the study of evolutionary arms races.