Inherent preference restricts host preference switching to a low-quality host in the generalist parasitoid wasp, Scleroderma guani.

Hymenopterous parasitoids serve as important biocontrol agents, offering a unique opportunity to investigate transgenerational effects in host adaptation. The phenotype and experiences of maternal wasps can influence various traits in their offspring, potentially influencing host-switching dynamics. Here, the inherent host preferences were explored in two colonies of a parasitoid Scleroderma guani, reared on Monochamus alternatus and Saperda populnea beetles respectively. The inherent influence of rearing history and maternal wasp experience on host preference plasticity is further discussed. The Monochamus alternatus-reared colony maintained an inherent preference for Monochamus alternatus while the Saperda populnea-reared colony showed a neutral tendency. These inherent preferences drove inter-colony differences in host preference plasticity, constraining preference shifts toward the lower-quality host Saperda populnea. Subsequently, a host-exchange experiment spanning five generations revealed a fitness-dependent preference shift when Saperda populnea-reared wasps were reared on Monochamus alternatus: the transition to Monochamus alternatus (a higher-quality but more defensive host) was postponed until maternal wasps adapted to host resistance by the fourth generation. In this case, Scleroderma guani presented an adaptive host preference shift strategy in consideration of ancestral experiences and fitness, providing insights into how generalist wasps maintain selective host preferences. These findings also have practical implications for optimizing artificial breeding of Scleroderma guani to enhance its efficacy in biocontrol against Monochamus alternatus, the primary vector of pinewood nematode. © 2025 Society of Chemical Industry.