Social parasitism: emergence of the cuckoo strategy between pseudoscorpions

Social parasitism is an intriguing model of arms-race coevolution, in which the parasite exploits the host social system. The parasite evolves to breakdown the host’s defenses. We analyzed the role of 2 pseudoscorpion species that live in mixed colonies in the Brazilian Cerrado (tropical savannah). Multispecies aggregation is a rare phenomenon among arachnids. Mixed pseudoscorpion colonies were studied in nature and in the laboratory during a period of 7 years and the hypothesis of a relationship based on social parasitism between species was evaluated, including the main strategies involved. Experiments and direct behavioral observations indicated that the pseudoscorpion Parachernes melanopygus is a social parasite of Paratemnoides nidificator, able to invade host colonies and exploit their resources by simulating host nymphs’ behavior. Although the host species has a recognition system, the parasite evades colony defenses by using a chemical camouflage mechanism. We find support for the hypothesis of a new model of social parasitism among phylogenetically distant pseudoscorpion species. To survive in the host colony, the parasite applies a combination of strategies, previously observed in social brood parasite ants and birds. This phenomenon provides new knowledge of the Arachnida group and also for known models of social parasitism.