Abstract

The terrestrial slugs Ambigolimax valentianus (Limacidae) and Deroceras leave (Agriolimacidae) are significant agricultural pests globally. Their widespread distribution is largely driven by anthropogenic activities, particularly the international trade of plant materials and soil containing their eggs or juveniles. Although these species are designated as Alert Alien Species in Korea considering the potential threat to native ecosystems, their presence in the field has not been officially verified so far. Here, we report the first confirmed occurrence of A. valentianus and D. laeve in South Korea based on morphological characteristics and molecular analysis of the cytochrome c oxidase subunit I (COI) gene. Specimens were collected from various regions in South Korea, humid habitats near human dwellings. Our findings suggest that these invasive slugs may have already established populations in Korea, highlighting the need for continuous monitoring and management strategies.