Larval density-driven cannibalism shapes trade-offs among development, flight, and reproduction in Spodoptera frugiperda

Understanding how population density influences the biological traits of migratory pests is essential for predicting their spread and developing effective control strategies. While cannibalism is a well-documented survival behavior under high-density conditions, its physiological consequences remain poorly understood. Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), a globally invasive pest with high reproductive and migratory capacity, displays substantial behavioral and physiological plasticity in response to population stress. In this study, we investigated the effects of density-induced cannibalism on flight and reproductive traits in S. frugiperda using integrated biological assays and multi-omics approaches. Cannibalism significantly accelerated larval development and enhanced energy production; however, it resulted in long-term fitness costs, including reduced fecundity, impaired flight performance, and shortened adult lifespan. Integrated transcriptomic and metabolomic analyses revealed a coordinated physiological reallocation under cannibalistic stress, particularly in females. Notably, 20-hydroxyecdysone (20E) was upregulated in larvae, facilitating rapid molting, while both juvenile hormone III (JH III) and 20E were markedly downregulated in adults, corresponding with suppressed reproductive and flight capacities. These results suggest that early-life density stress triggers hormonal reprogramming that promotes immediate developmental benefits at the expense of adult performance. Our findings shed light on the life-history trade-offs associated with cannibalism and provide new insights into the ecological adaptability of S. frugiperda, offering a foundation for density-responsive pest management strategies.