Control interventions against mosquito larvae are the primary measure to reduce the adult abundance and risk of arbovirus outbreaks in Europe. One of the most commonly used larvicides in Italy is diflubenzuron (DFB), which targets chitin synthase 1 (chs-1), interrupting the normal development of larvae into adults. Recent studies identified high levels of DFB resistance in Culex pipiens populations from Emilia-Romagna (Italy) associated with I1043L/M/F mutations at position 1043 of the chs-1 gene. The aim of the present study was to assess the circulation of 1043 resistance alleles in Cx. pipiens populations across Italy, outside Emilia-Romagna, with a focus on the Veneto region. Overall, 1032 specimens were genotyped. The 1043L allele was found in all examined Italian regions (Trentino-Alto Adige 19–36%; Veneto 0–91%; Piemonte 11%; Liguria 28%; Lazio 0–8%; Puglia 5%). The highest frequencies (up to >90%) were observed in the Venetian lagoon, where 1043M was also detected (6–11%). Overall, the relatively low frequencies of 1043 mutations despite extensive and longstanding use of DFB in Italy suggest a high fitness cost worthy of further investigations, while their extremely high frequencies in coastal touristic sites point to these sites as the most relevant for resistance monitoring and larvicide rotation.

Animal behaviour in human‐dominated landscapes is difficult to study at large spatial and temporal scales, especially for small species characterised by elusive movements. Citizen science can help overcome these limitations by turning routine human–animal encounters into observations of where and when species are active. Here we exploited the Mosquito Alert citizen science platform to study the indoor versus outdoor presence of Aedes albopictus (generally considered as predominantly exophagic/exophilic) in contrast with sympatric Culex pipiens . We analysed 21,433 expert‐validated photographic records of Ae. albopictus and Culex spp. from Italy and Spain (2021–2024) classified by Mosquito Alert contributors as taken indoors or outdoors. We combined descriptive statistics with generalised linear and additive mixed models to (i) quantify species‐specific probabilities of indoor records and (ii) estimate the relative contribution of Ae. albopictus to indoor mosquito records. We complemented the citizen science results with two small‐scale indoors versus outdoors entomological collections carried out in Italy in August–September 2024. Overall, 56% and 91% of Ae. albopictus and Culex spp. records were classified as indoor, respectively. The modelled probability that an Ae. albopictus record referred to a specimen photographed indoors averaged 56.3% (95% CI: 49–63) and increased from 40% to 50% in late spring to ~60% in late autumn. In contrast, the probability of Culex spp. indoor records remained consistently >90%. Among indoor records, the probability that a photographed specimen was Ae. albopictus averaged 61.8% (95% CI: 58.7–64.9) and peaked at 73.4% (95% CI: 70.6–76.0) in midsummer. Results from the small‐scale field assessments show observed daily mean female Ae. albopictus indoor ratios of ~22% and ~27% in the two study sites. These results provide a first estimate of indoor presence of Ae. albopictus in its invasive range in Europe. Even accounting for the biases associated with this citizen science data, results show that the probability of coming into contact with Ae. albopictus indoors is not negligible, with relevant implications for epidemiological studies, vector control and public health. Moreover, the study highlights the potential of citizen science platforms to act as observatories for wildlife living in close association with humans, revealing behavioural patterns not assessable otherwise. Read the free Plain Language Summary for this article on the Journal blog.

Aedes invasive mosquito (AIM) species are expanding worldwide, increasing the risk of arbovirus introduction and transmission. Points of Entry (PoEs), including airports and seaports, represent critical gateways for the introduction and spread of invasive vectors through international passenger and cargo traffic. This study evaluated the AIM long-term dynamics at three major PoEs (Treviso Airport, Venice Airport, and Venice Port) in northeastern Italy (Veneto region) between 2018 and 2024 through an integrated entomological surveillance programme designed to collect AIMs (adults and eggs) throughout the seasonal activity (June–October). Mosquitoes were identified morphologically and, where required, by molecular analyses. Aedes albopictus was the dominant AIM throughout the study period (eggs N = 96,192, adults N = 14,231), being detected at all three study sites and showing consistent interannual and seasonal dynamics, with peak abundance during summer despite routine vector control interventions. Aedes koreicus was detected at two of the three study sites, namely Venice and Treviso airports (eggs N = 1, adults N = 3). Phylogenetic analyses based on COI indicated that these specimens belonged to a distinct European lineage, revealing genetic diversity among European populations of Ae. koreicus. No evidence of newly established AIMs was found during the surveillance period. These findings highlight the importance of long-term surveillance at PoEs for the early detection of AIMs, monitoring temporal changes in established vector populations, and supporting integrated control and surveillance strategies to reduce the risk of vector establishment and mosquito-borne disease transmission.