Colonisation and temperature-driven variation in life-history traits of the West Nile virus vector Culex pipiens at its northern European limit

•Background: Mosquito-borne diseases (MBDs) are increasing worldwide driven by factors such as travel, land-use change, global trade, and climate warming. In Europe, Culex pipiens sensu lato (s.l.)—the primary vector of West Nile and Usutu viruses—is widespread and an increasing public-health concern with recent detection of WNV in English mosquitoes and ongoing climate change underscoring risks in northern regions. However, data on how temperature affects life-history traits of high-latitude populations remain limited, hindering accurate predictions of vectorial capacity. •Methods: We used field-collected larvae in Scotland to establish a colony of Culex pipiens and performed its molecular characterisation by PCR, including Wolbachia presence. We then assessed the effects of temperature on key life-history traits, including development time, adult longevity, and body size. •Results: We successfully established a colony of Culex pipiens pipiens infected with Wolbachia at its northern range limit. We observed that temperature increase speeds up the embryonic, larval and pupal development while reducing the adult longevity and adult size. Interestingly, this northern colony display the longest adult survival ever described for non blood fed Cx. pipiens at all temperature examined. •Conclusions: Our findings provide critical baseline data for this northern population and offer methodological guidance for establishing Cx. pipiens colonies from field material. These results improve our understanding of thermal sensitivity in Northern Culex mosquitoes and will support future modelling of population dynamics and MBD risk under climate change.