Diversity and associations of parasites, parasitoids, and nest-associated organisms of <i>Vespa mandarinia</i> (Hymenoptera: Vespidae) in South Korea

The northern giant hornet ( Vespa mandarinia Smith, 1852) is a dominant eusocial wasp species in East Asia; however, knowledge of organisms associated with its colonies, including parasites and other nest-associated taxa, remains limited. To address this gap, this study investigated the diversity and ecological roles of organisms associated with V. mandarinia colonies and individuals in South Korea using a combination of morphological examination and DNA barcoding analyses. A total of seven associated species were identified: Xenos moutoni (du Buysson, 1903) (Strepsiptera: Xenidae); Volucella suzukii Matsumura, 1916 and Vo . coreana Shiraki, 1930 (Diptera: Syrphidae); Pyralis regalis (Denis &amp; Schiffermüller, 1775) (Lepidoptera: Pyralidae); Pheromermis vesparum Kaiser, 1987 (Nematoda: Mermithidae); Quedius pectinatus (Sharp, 1874) (Coleoptera: Staphylinidae); and Hermetia illucens (Linnaeus, 1758) (Diptera: Stratiomyidae). These species exhibited distinct ecological associations with V. mandarinia . X . moutoni was confirmed as an obligate endoparasite that induces behavioral and reproductive alterations in its host. Vo . suzukii , Q . pectinatus , and H . illucens were primarily associated with nest-derived detritus beneath hornet nests and exhibited scavenger-like behavior, with no evidence of direct predation on host individuals, suggesting predominantly commensal associations. In contrast, Vo. coreana was consistently associated with the comb and nest cells, suggesting a more exploitative ecological strategy. P . regalis primarily consumed nest material and meconium and occupied an intermediate ecological position between a facultative predator and a nest-associated organism. Ph . vesparum , recorded for the first time in Korea and Asia, was detected in only a single V. mandarinia individual, suggesting a negligible impact on hornet populations under natural conditions. Overall, this study provides baseline taxonomic and ecological data on parasites and nest-associated organisms associated with V. mandarinia in Korea and highlights the ecological complexity of hornet nests as microhabitats that support diverse symbiotic assemblages. These findings serve as a foundation for future research on the life histories, host interactions, and potential functional roles of nest-associated organisms in hornet colony dynamics.