Abstract: This study investigated the natural population dynamics of the invasive fall webworm, Hyphantria cunea (Drury), and evaluated regulatory effects of natural enemies across different regions, generations, and developmental stages. We established age-specific life tables for H. cunea populations exhibiting 2–3 annual generations in Tieling, Dandong (Liaoning Province), and Anyang (Henan Province) from 2022 to 2024. Mortality rates were systematically analyzed focusing on parasitism and predation impacts. Key results indicated that: (1) Population trends: Population Trend Index (I) for H. cunea exceeded 1 across all three regions during 2022–2024, indicating sustained population growth. Spatial/generational variations showed Tieling > Anyang > Dandong (same generation) and 1^stG (first generation) > 2^ndG (second generation) > OG (overwintering generation; same year). Population dynamics followed “suppressed first generation populations post-overwintering” in bivoltine regions and “lower abundance in the first generation, higher in the second, and most severe in the overwintering generation” in trivoltine regions. (2) Natural enemy efficacy: Predators caused significantly higher mortality (24.8–40.3%) than parasitoids (8.0–11.8%) (p < 0.05), generation-specific analysis revealed a significant hierarchy in biocontrol efficacy: 1^stG ≈ 2^ndG < OG, with overwintering generations exhibiting peak suppression. (3) Key controls: Natural loss and predation were pivotal, with larval-stage management being critical. This study clarifies that natural enemies constitute the primary limiting factor for H. cunea populations, exhibiting a “following phenomenon” correlated with outbreak severity. It confirms that natural enemies alone are insufficient to contain pest invasion spread in real-world scenarios. Furthermore, the study distinguishes the suppression efficacy between predatory and parasitoid natural enemies across pest generations, revealing distinct control patterns at different developmental stages. These advancements redirect the discipline’s focus from “solely exploring natural enemy resources” to “deciphering dynamic interactions between natural enemies and invasive pests”, thereby providing pivotal theoretical support for refining both the Natural Enemy Limitation Theory in invasion biology and the Ecological Regulation Strategy in biological control practices.

Key words: Hyphantria cunea , Natural enemy, Population dynamics, Key factor analysis, Age-specific life table