Phenology and parasitism rates of Xenos oxyodontes and Xenos moutoni (Strepsiptera: Xenidae) in Vespa (Hymenoptera: Vespidae) in South Korea.

The long-term seasonal parasitism patterns, hereafter referred to as stylopization, and within-nest developmental stage distributions of Vespa-associated Xenidae (Strepsiptera) remain poorly characterized in South Korea. We compiled 15 years of data (2008-2023) based on trapped Vespa individuals from multiple regions and quantified stylopization rates for two Xenidae species, Xenos oxyodontes and Xenos moutoni, based on diagnostic characters visible on stylopized hosts. Seasonal occurrence was summarized primarily from female Xenos specimens, which can be identified to species, and host-association patterns were assessed where possible. To complement the trap-based records, we dissected 22 Vespa analis colonies collected in September 2020 and documented strepsipteran developmental stages within the nests. Across 39,610 examined host individuals, stylopization rates and seasonal occurrence differed between the two Xenos species and among host taxa, indicating distinct host-use and temporal activity patterns. Importantly, the nest dissections provided direct observations of late-season developmental stage compositions, enabling us to compare within-nest reproductive/developmental stages to those inferred from trap-detected stylopized hosts. This comparison revealed that key reproductive-stage information may not be captured by trap records alone. Thus, integrating long-term trap data with nest-level observations can clarify species-specific phenology and developmental/reproductive stage distributions in Vespa-associated Xenidae, providing a better empirical context for interpreting stylopization intensity and developmental timing in field populations.