Distribution: C. torrentium is a Palaearctic species, distributed in Northern and Central Europe, Asia Minor, Iran and extending eastwards as far as western Siberia (Cranston et al. 1987, Schaffner et al. 2001).

Habitat: Aquatic stages may be encountered in a variety of breeding sites, including rock holes, pools along torrents, water puddles and watersides of ponds, or artificial habitats like tires, barrels and containers (Mohrig 1969, Briegel 1973, Cranston et al. 1987, Schaffner et al. 2001, Becker et al. 2003). The water can be fresh or brackish, very dirty or rich in iron oxide; the sites are generally small, open or under a forest canopy, lacking underwater vegetation; larvae are often associated with those of C. pipiens (Schaffner et al. 2001). Contrary to C. pipiens, C. torrentium is adapted to lower water temperatures and dominates in cold regions or at higher altitudes (Mohrig 1969, Schaffner et al. 2001). Moreover C. torrentium is the only Culex species recorded from natural tree holes (Onyeka 1980).

Biology: The species is multivoltine; eggs are laid on the water surface and larvae are present during the summer, from spring to the beginning of autumn (Schaffner et al. 2001). According to Becker et al. (2003) the larval development seems to be slower than in C. pipiens, which may result in only one generation per year in northern countries. Adults are present during the summer until the first frosts. C. torrentium overwinters as fertilized, diapausing females in shelters, such as hollow tree trunks, caves or cellars (Cranston et al. 1987, Schaffner et al. 2001).

Adults: Adults have been observed feeding on flower nectar, mostly at night; females are considered as ornithophilic; they are vectors of the Sinbis virus (Ockelbo) (Service 1968b, Schaffner et al. 2001). The species has never been recorded to bite man (Becker et al. 2003).