Spodoptera frugiperda is a newly invasive pest in China, often sharing the same feeding niche with native S. exigua. To clarify the competitive displacement, colonization and potential threat to crops by S. frugiperda, the cannibalism and predation behavior, feeding preferences, development and reproduction of both species under laboratory conditions, as well as the population dynamics and damage to maize plants in the field, were studied. Results found that food scarcity intensified interspecific predation between S. frugiperda and S. exigua, but the survival rate of 4th instar S. frugiperda was not significantly influenced (> 93%; P > 0.05). Although S. frugiperda exhibited less aggressive behaviors, its cannibalism coefficient and attack intensity were significantly higher than those of S. exigua (P < 0.05). Moreover, S. frugiperda showed a higher feeding preference for mechanically lethal insects when the maize leaf supply was insufficient. Additionally, a combined diet of maize leaves and lethal insects significantly increased their pupal weight and fecundity (P < 0.05). Field trials showed that when S. frugiperda and S. exigua co-occurred, the population of S. frugiperda at mature stage was similar to that after the intraspecific treatment, and seriously damaged maize plants. These results suggested that interspecific predation by S. frugiperda on S. exigua not only conferred an obvious advantage, but may also promote its development and reproduction, and facilitated its colonization in the invaded area. Our results provide an understanding of the rapid colonization mechanisms of S. frugiperda and will assist development of integrated management strategies.

草地贪夜蛾(Spodoptera frugiperda)是我国的一种新入侵害虫，经常与本土甜菜夜蛾共享相同的取食环境。阐明草地贪夜蛾的竞争性迁移、定殖和对作物的潜在威胁、同类相食和捕食行为、取食偏好、实验室条件下这两个物种的发育和繁殖，以及田间玉米植株的种群动态和损害，进行了研究。结果发现，食物匮乏加剧了草地贪夜蛾和甜菜夜蛾的种间捕食，但对4龄草地贪夜蛾的存活率影响不显着（>93%； P >0.05）。虽然草地贪夜蛾的攻击行为较少，但其同类相食系数和攻击强度均显着高于甜菜夜蛾（ P < 0.05）。此外，当玉米叶供应不足时，草地贪夜蛾对机械致死昆虫表现出更高的取食偏好。此外，玉米叶和致死昆虫的组合饮食显着增加了蛹的重量和繁殖力（ P <0.05） 。田间试验表明，当草地贪夜蛾与甜菜夜蛾共生时，成熟期草地贪夜蛾种群数量与种内处理后相似，对玉米植株造成严重损害。这些结果表明，草地贪夜蛾对甜菜夜蛾的种间捕食不仅具有明显的优势，而且可能促进其发育和繁殖，有利于其在入侵地区的定殖。 我们的结果提供了对草地贪夜蛾快速定植机制的了解，并将有助于制定综合管理策略。