Changes in gut microbiota of Loxostege sticticalis (Lepidoptera:Pyralidae) at different diapause stages

Loxostege sticticalis,belonging to the family Pyralidae in the order Lepidoptera, is a major migratory pest in the agro-pastoral ecotone of Eurasia, which can survive harsh winters and food shortages through diapause. Although gut microbiota have been shown to play a crucial role in insect environmental adaptation, their succession patterns and functions during diapause in L.sticticalis remain unclear. This study used 16S rRNA sequencing to analyze the succession patterns of the gut microbiota in L.sticticalis at the prediapause (PD), diapause (D1, D3, and D5, diapause for 1, 3, and 5 months), and post-diapause quiescence (PDP) stages. The results showed that the gut microbiota underwent significant dynamic reorganization during diapause maintenance: diversity is at lowest in the PD stage, however, it rapidly recovered, and eventually stabilized during diapause stage. Bacteroidetes dominated the initial community, while Actinobacteriota abundance gradually increased with the extension of diapause and became the dominant bacterial phylum during the PDP stage. Functional predictions showed that the bacteria related to lipid and amino acid metabolism, which may help the host accumulate energy to cope with starvation during diapause; while at the PDP stage, the microbiome was enriched in taxa that contribute to nitrogen cycling, likely assisting in the recycling of endogenous nitrogen to support the upcoming pupation and metamorphosis. In conclusion, L.sticticalis actively changes the proportion of gut bacteria to store and release energy, and to promote nitrogen absorption or recycling. Gut bacteria facilitate host adaptation to environmental stress via metabolic compensation, revealing synergistic insect-microbe adaptation during diapause. This study provides a theoretical foundation for new, eco-friendly pest control strategies.