Predator egg‐induced non‐consumptive effects suppress spider mite survival and reproductive performance

BACKGROUND Predators suppress pest populations not only through direct consumption but also via non‐consumptive effects (NCEs), in which prey perceive predation risk and alter behaviors, physiology, and life‐history strategies. Despite the growing recognition of the importance of NCEs in biological control, most studies focus on cues from actively feeding predators, while the role of non‐feeding stages, such as predator eggs, remains poorly understood. Here, we investigated whether eggs of the predatory mite Phytoseiulus persimilis function as intensity‐dependent risk cues that influence the performance and population growth of the invasive spider mite Tetranychus ludeni . RESULTS Exposure to P. persimilis eggs significantly altered T. ludeni life‐history traits in a density‐dependent manner, even in the absence of direct predation. Increasing predator egg density reduced female longevity, reproductive rate, and total fecundity, delayed reproductive onset, but accelerated early egg production. Exposure to predator eggs also generated pronounced transgenerational effects that prolonged egg and female offspring development, reduced egg hatching, and lowered immature survival. These individual‐level responses translated into strong population‐level consequences, which significantly decreased the net reproductive rate ( R 0 ), intrinsic rate of increase ( r m ), and finite rate of increase ( λ ), but increased population doubling time ( Dt ) as predation stress intensified. CONCLUSION Our results demonstrate that predator eggs induce intensity‐dependent NCEs that significantly suppress spider mite population growth. By extending fear‐mediated effects from non‐preying predator stages, this study broadens the functional scope of biological control and highlights the ecological significance of early predator cues in regulating pest populations.