Egg mass scale thickness: Multifunctional maternal defenses driving niche expansion and global pest status of Spodoptera spp

Abstract

Background : The genus Spodoptera (Lepidoptera: Noctuidae) includes some of the most destructive agricultural pests globally, such as S. frugiperda , S. litura , and S. exigua . Following oviposition, female moths cover their egg masses with abdominal scales, forming a protective layer whose thickness varies among species and individuals. This trait may enhance egg survival and contribute to pest outbreaks, yet its morphological characteristics and ecological significance have not been systematically reviewed. Methods : This review synthesizes the available literature to integrate current knowledge on the morphological characteristics and ecological functions of egg mass scale-layer thickness in Spodoptera , with particular emphasis on its implications for integrated pest management (IPM). Results : The scale layer functions as a multifunctional barrier that protects eggs from natural enemies, mitigates abiotic stresses, and may reduce susceptibility to microbial pathogens and chemical insecticides. This defensive trait appears to favor specialist egg parasitoids such as Telenomus remus over generalist Trichogramma species, while simultaneously reducing the efficacy of contact ovicides. Conclusion : Egg mass scale-layer thickness represents a key behavioral adaptation that enhances egg survival and reduces egg-stage mortality, thereby contributing to the ecological success, invasion potential, and global pest status of Spodoptera species. A deeper understanding of this trait may provide a valuable foundation for improving biological and chemical control strategies targeting these pests.