Mothers know best: spatial and nutritional limitations shape offspring performance in the predator mite <i>Amblyseius herbicolus</i>

Abstract Rearing conditions play a crucial role in shaping the life-history traits of arthropods, yet the combined effects of rearing environment and prey availability within and across generations remain poorly understood. This study investigated how rearing cell size (large vs small) and prey availability (30 vs 60 Carpoglyphus lactis eggs per day) influence the performance of the predatory mite Amblyseius herbicolus and its offspring under controlled laboratory conditions. Within the maternal generation, individuals confined to small cells consumed significantly more prey but showed no improvement in development, survival, or adult size, indicating stress-related increases in energy expenditure. High prey availability enhanced survival rate, and its interaction with cell size revealed that high prey availability mitigated the negative effects of stress. Under high prey availability, mothers in small cells produced remarkably larger eggs, suggesting altered reproductive investment under stress. Across generations, offspring of mothers reared under low prey availability and small rearing cell size showed higher survival and larger adult size, reflecting compensatory maternal effects. These findings partially support the hypothesis that restricted rearing environments and low prey availability negatively affect within-generation performance but promote adaptive transgenerational responses, providing new insight into maternal effects and rearing optimisation in phytoseiid predators.