Résumé
Several species of Lepidoptera with caterpillars bearing urticating hairs are increasing their range in metropolitan France from year to year, such as the pine processionary (Thaumetopoea pityocampa Denis et Schiffermüller 1775) whose presence was historically limited to the south of France, and which is gradually being observed in the north and at higher altitudes. The procession period also seems to be appearing earlier. Climate change could have an impact on the range and phenology of this species, as well as other species of Lepidoptera with caterpillar bearing urticating hairs. Urticating caterpillars, which can trigger diffuse urticariform papules and allergic reactions for human people through contact with the skin, mucous membranes or inhalation, represent a health issue. These caterpillars also cause a health risk for animals and can have an impact on plants due to the resulting defoliation. This risk assessment therefore focused on the risk posed by these urticating caterpillars in areas where they have been established for a long time as well as in areas where they currently do not occur but could be colonized in the short or medium terms. One of the outputs of the evaluation consisted in identifying 55 different species of Lepidoptera with urticating caterpillars, for metropolitan France, but also for the overseas regions, based on the review by Kawamoto and Kumada (1984) and the GBIF database. In addition, detailed sheets for the well‐known species were drawn up, describing in particular their range, their phenology and the period when the urticating stages occur. A literature review as well as data from poison control centres and the analysis of the results of two surveys (of three associations of dermatologists/allergists and of occupational populations at risk) allowed to characterize the contexts of exposure and the human populations at risk. Concerning animal health, in addition to an epidemioclinical description based on the literature, data from veterinary poison control centres were analyzed in the specific case of dog exposure to the pine processionary between 1999 and 2021 in metropolitan french territory. Given the impact of these species of Lepidoptera on ecosystems, due to the defoliation they induce, this scientific opinion investigated the impact of these species on ecosystem services. The socio‐economic impacts of defoliations and risk management measures implemented in the event of an outbreak were studied based on a literature review and simulations for forest recreation. To represent risk for the whole metropolitan France territory, three risk maps of the human population exposure to the pine processionary, the oak processionary and the brown‐tail moth were designed at municipality level. A multi‐criteria analysis was undertaken to characterize danger (urticating caterpillars) and vulnerability of human populations. Then, the municipalities were ranked according to their level of danger and vulnerability. As a result, municipalities have been classified into 5 danger classes and 5 vulnerability classes. Based on a risk matrix with levels of hazard (abscissa axis) and levels of vulnerability (ordinate axis), 5 levels of risk were finally defined and the 34,816 municipalities of metropolitan France were classified according to their level of risk.