Early detection of exotic mosquito species (EMS) is of vital importance to prevent potential local transmissions of mosquito-borne diseases. Since 2007, the introduction of EMS in Belgium, especially Aedes species, is investigated during successive nationwide active entomological monitoring focusing on Points of Entry (PoE; i.e. locations where introductions of EMS can be expected). In 2022, passive monitoring through citizen science was added to increase the spatio-temporal coverage for new detections of the Asian tiger mosquito (Aedes albopictus) also outside PoEs. This species is spreading northward in Europe, with Belgium being at the front of its invasive range. It was found to enter Belgium repeatedly and increasingly over the last decade through different introduction pathways, with twice as many positive locations (PoEs and residential areas) in 2023 compared to 2022, and even some overwintering. In order to delay the species´ spread and establishment, accurate and reliable species-level ...