Is Aedes albopictus truly exophagic in Italy? Citizen science data can tell

In its native range in Asia, the tiger mosquito, Aedes albopictus, bites mostly outdoors. This is a major behavioural difference compared to Aedes aegypti and one of the reason of the Ae. albopictus lower synanthropy and lower efficiency as vector of human arboviruses. However, whether this exophagic behaviour is maintained also by Ae. albopictus invasive populations after adaptation to temperate climates has never been specifically investigated. We here exploited 4,914 photographic records provided by citizen during 2-years implementation of Mosquito Alert app in Italy to investigate indoor/outdoor contacts between Ae. albopictus and humans relatively to Culex pipiens. Aedes albopictus represented 90% and 52% of the total number of mosquitoes photographed outdoors (N=1,087) and indoors (N=1,842), respectively. Despite the total number of mosquitos recorded indoors vs outdoors is likely biased by the higher difficulty of taking a picture outdoors, the observation of such a high proportion of Ae. albopictus among mosquitoes recorded indoors represents an objective evidence of a strong endophagic activity of this species in Italy. This may reflect a change in the species behaviour with a high epidemiological relevance, as it implies a higher contact with humans than that estimated by data obtained by conventional outdoor collection methods. Moreover, it may imply a change in practices to prevent arbovirus transmission, i.e. no longer personal protection only, but also protection of the indoor environment. Finally, the results show the exciting capacity of citizen science in providing original data in revealing biological aspects difficult to be investigated by conventional monitoring approaches.