In the present study, we report the first complete mitochondrial DNA genome of the genus Callipogon based on C. relictus, a natural monument and endangered species in South Korea. The mitogenome is 15,742 base pairs with 13 protein coding genes (PCGs), two rRNAs, 22 tRNAs, and a 1033 bp long AT-rich region. The overall base composition was 67.3% AT and 32.7 GC. Among 13 PCGs, seven genes (Nad2, Atp8, Atp6, Nad4L, Nad6, Cob, Nad1) harbour the typical stop codon TAA or TAG, whereas remaining five genes terminate with T. Interestingly, Cox3 employs AGA as the termination codon.

A complete taxonomic assessment of the inquiline fauna (Hymenoptera: Cynipidae: Synergini, Ceroptresini) reared from cynipid oak galls collected in South Korea is conducted for the first time. Previously, six species were known from this country (Ceroptres kovalevi Belizin, 1973; Synergus chinensis Melika, Ács & Bechtold, 2004; Synergus japonicus Walker, 1874; Ufo koreanus Melika, Pujade-Villar & Choi, 2007; and presumably, Saphonecrus chaodongzhui Melika, Ács & Bechtold, 2004 and Ufo cerroneuroteri Tang & Melika, 2012). The study of new material reared from cynipid galls collected from oaks (Quercus spp.) from various locations throughout South Korea has increased the total number of inquiline species known from this country to 14, of which seven are new country records (Saphonecrus shirakashii (Shinji, 1940); Sa. symbioticus Melika & Schwéger, 2015; Synergus abei Melika & Schwéger, 2015; S. belizinellus Schwéger & Melika 2015; S. formosanus Schwéger & Melika, 2015; S. ishikarii Melika & Schwéger, 2015; and S. symbioticus Schwéger & Melika, 2015), and one is a new species: Synergus minutus Lobato-Vila & Pujade-Villar, sp. nov. The new species is formally described and illustrated. New biological and distribution data are provided for both the newly recorded species and the other reared species. The Korean fauna is compared with that from other countries within the Eastern Palearctic and the Oriental regions.

Pine wilt disease in Korea can be managed by reducing vector density through chemical application. To reduce the side effects from pesticides, effective natural enemies must be identified and used to reduce the vectors’ natural density. Sentinel logs were used to investigate a parasitoid wasp parasitic to Monochamus alternatus and Monochamus saltuarius, the vectors of Bursaphelenchus xylophilus, which causes this disease. During 2016–2017, the parasitoid wasps distributed in the Pinus densiflora and Pinus koraiensis forests were surveyed using sentinel logs at six different areas. An ectoparasitoid wasp Spathius verustus Chao of M. alternatus and M. saltuarius was identified. We showed for the first time that S. verustus was parasitic to M. alternatus in South Korea and to M. saltuarius worldwide. The parasitism rates were affected by region and session but not by the sentinel log height in the tree and the distances between the trap and forest edge locations. Studies also showed that S. verustus appeared to prefer M. alternatus to M. saltuarius as a host. This study unveiled the ecological details of S. verustus. Further research on various environmental factors such as regional differences, host density differences, and the degree of damage from the pine wilt disease is required to understand the effects of environmental or ecological factors on parasitism rates.

The invasive hornet Vespa velutina Lepeletier, which first invaded South Korea in 2003, has spread throughout the country, significantly affecting apiaries, ecosystems, and human health. Xenos spp. (Xenidae, Strepsiptera) are primarily parasitic to social wasps, with V. analis being the only known host in Korea. Until recently, no parasites or parasitoids on V. velutina had been discovered. In 2020, strepsipteran parasites were discovered on 11 hornet workers in Andong City, South Korea. These parasites, comprising four larvae and seven pupae, were all male, except for one individual of an undetermined sex. Molecular analysis and morphological examination identified the parasites as Xenos moutoni (du Buysson, 1903) and X. oxyodontes Nakase & Kato, 2013. This marks the first recorded instance of strepsipteran parasites on V. velutina in regions invaded by this hornet. Although the exact infection rate of these parasites could not be determined, it appears that native strepsipteran parasites have adapted to a non-native Vespa species. Stylopization, the condition caused by these parasites, is known to negatively affect hornet colonies: infected workers do not contribute to nest activities, hindering nest development, and infected reproductive individuals (males and new queens) do not mate, which impedes the establishment of new colonies. However, due to the hornet’s high reproductive rate and compensatory mechanisms, the overall control effect of the parasites is likely to be minor.

For the first time, Bethylus Latreille, the type genus of Bethylidae (Hymenoptera, Chrysidoidea, Bethylinae), is reported from the Korean Peninsula based on the discovery of a new species, Bethylus colligatussp. nov., which was collected in Gangwon Province near the Demilitarized Zone. This new species is described and illustrated. A phylogenetic analysis was conducted using mitochondrial cytochrome c oxidase subunit I sequences from common Bethylus species to better understand the evolutionary relationships within the genus. The resulting phylogeny supports the distinction between B. colligatussp. nov. and other species. Additionally, a key to the species of Bethylus in East Asia is provided.