Cx. pipiens is one of the major vectors of West Nile virus in the south of Russia and it is represented by the autogenic form, molestus, and the non-autogenic form, pipiens. The spatial distribution of its larvae and food preferences of females was investigated to assess the potential role of each form in the spread of the virus. The taxonomic status of the mosquitoes was determined from their capacity for autogenicity (543 specimens) and the type of mitochondrial DNA (348 specimens). The mosquitoes of the pipiens form were shown to develop in the open urban and rural reservoirs and the females were non-autogenic. Cx. pipiens form molestus was found only in the urban biotopes, mainly in the flooded basements and, in some years, also in the open reservoirs where it formed a mixed population with Cx. pipiens form pipiens. Both autogenic (85-95.2%) and non-autogenic specimens were identified among the females with the mitotype in form molestus. Genetic analysis of Cx. pipiens females collected under the Berezantsev bell and in the trap with a bird showed that both forms were attracted to man and the bird. The findings suggest that Cx. pipiens form pipiens can transmit West Nile virus to humans both in the town and in its suburb and Cx. pipiens form molestus can only in urban areas.