First record of <i>Pachodynerus nasidens</i> (Latreille) (Hymenoptera: Vespidae) for the western Palaearctic region

Pachodynerus nasidens (Latreille), mud or keyhole wasp, is a Neotropical species that has been expanding beyond its native range. In addition to America, it has successfully established populations in the Pacific islands, Japan, and Australia. This study reports the first confirmed record of P. nasidens in the western Palaearctic region, specifically in Madeira Island, making it the first occurrence of an introduced species of Vespidae in Madeira Island and the second in Macaronesia. The spread of P. nasidens is likely facilitated by human-mediated transport, particularly through aviation and maritime activities. The species' remarkable nesting plasticity, which allows it to exploit pre-existing cavities, other wasps' nests and burrows, is suggested to play a key role in its successful colonization of new insular environments. Given the ecological uniqueness of Madeira, further research is needed to assess potential ecological impact of this introduced species, particularly regarding its potential competition with the endemic cavity-nesting wasp Ancistrocerus madaera (de Saussure, 1853).