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 identification of all life stages is essential. Therefore, DNA-barcoding was applied to validate the morphological identifications of Ae. albopictus . This technique has proven its usefulness especially regarding the identification of Aedes eggs. The cytochrome c oxidase subunit I (COI) genetic diversity of 233 specimens (mainly eggs) was screened, with one dominant haplotype (H1; N TotalHap=13) recorded within more than 170 specimens collected over all investigated locations (sequences deposited on GenBank, extracted DNA dried for long-term preservation in RBINS collections). When including sequence material from online repositories, the minimum spanning network revealed no association between haplotypes and geography, but the haplotype composition in Belgium differed slightly between PoEs/residential areas. Unique haplotypes were identified at international import companies (lucky bamboo: H8,H9), at highway parking lots (H3,H10,H11), and in residential areas (H4,H7,H12,H13). Only H1 was largely shared between ...