Short photoperiod facilitates seasonal migration in Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), is an important invasive migratory pest that poses a serious threat to global food security. However, behavioral and physiological responses to seasonal changes in photoperiod have received little attention in FAW. Here, we present behavioral evidence that FAW under shorter photoperiods (12L:12D and 10L:14D) exhibited stronger flight capacity and pathogen resistance to Beauveria bassiana compared to those under longer photoperiods (16L:8D and 14L:10D), but weaker reproductive performance. After prolonged flight, shorter photoperiods facilitated the reproduction of flying females compared to the controls (nonflying moths), while longer photoperiods suppressed reproduction. Short photoperiod reduced larval mortality and pupal weight of FAW but increased adult emergence rate. Our results indicate that shorter photoperiods enhance the migration propensity for improved survival in FAW, and provide insights into how photoperiod controls seasonal changes in behavior and physiology that lead to seasonal adaptation in this globally important pest.