A new record of Culex restuans Theobald (Diptera: Culicidae) in British Columbia

Culex restuans is a New World mosquito species closely related to and resembling the cosmopolitan house mosquito Culex pipiens L. Typically, Cx. restuans lays its egg rafts on the surface of woodland pools, but it has adapted to lay its eggs in artificial containers. Immature stages can be found in water-filled containers from abandoned appliances to used tires that harbour algae. The immature stages of Cx. restuans can develop in water that ranges from clear to highly polluted. Like Cx. pipiens, the females obtain blood meals from birds, but can also feed on a broad range of mammal and reptile hosts (Hayes 1961). For that reason, the females have been identified every year since 2002 as a carrier and potential vector of West Nile virus (Ebel et al. 2005). Its life cycle is similar to our other Culex species. Those adults that eclose in the late summer and fall mate, but the females are in reproductive diapause and feed only on carbohydrates before overwintering. In rural hab i t a t s , t hey p robab ly sea rch ou t underground burrows and similar sites to hibernate, but in anthropic habitats, they are common in basements and outbuildings. Its known distribution in America ranges from the eastern half of Alberta south and east to Guatemala, and it is common in southeastern Canada and the eastern and central United States. There are fewer records in the west, although according to Darsie and Ward’s (2005) authoritative work, the insect’s range extends to the west coast through Wyoming, southern Idaho and Oregon. Wellsubstantiated records in southwestern California exist. We describe the first verifiable record of this species in British Columbia (B.C.) from a photograph taken by one of us (McCann) in Goldstream Provincial Park, on Vancouver Island, about 16 km northwest of Victoria, on 10 October 2010 (Fig.1). The Cx. restuans female was found under a bridge deck alongside Cx. tarsalis and Culiseta incidens females. Its pale abdomen was distended with hypertrophied fat body and it was probably ready to hibernate but unfortunately escaped capture. The paired patches of pale scales on the scutum, which were clearly visible, allow reliable differentiation of this individual from Cx. pipiens. The scutum of Cx. pipiens has never been reported with the pale spots or the pale scales that are clearly visible above the wings on the scutum of the female we photographed, confirming our identification. Three other records of this species in or close to B.C. have been explained as misidentifications or accidental introductions. The provincial record is of a female taken in a light-trap at Esquimalt (Twinn 1945). The specimen is lost, and Wood et al. (1979) considered it to be a misidentified Cx. pipiens. Further east, there are records of Cx. restuans near the northern border of the Idaho panhandle, just south of Creston, B.C. (State of Idaho 1985). There seem to be no specimens confirming these records. Darsie and Ward include their localities on the distribution map of the first edition of their monograph (Darsie and Ward 1981), but not in the second (Darsie and Ward 2005, Plate 29B). The third record is from Island County, in northwestern Washington, close to Seattle and Tacoma. Sames et al. (2007) point out that this record is “far outside the distribution range”—depicted in Darsie and Ward (2005) —and suggest that “this species may have been accidentally introduced into Island County” by tourists or from nearby ports. We believe our specimen lends credence to Twinn’s 1945 identification, because Esquimalt is within flying range (9 km) of Goldstream Provincial Park, and both are just across the Salish Sea (63 km) from Island County, WA. We suspect that these western records are from established populations that J. ENTOMOL. SOC. BRIT. COLUMBIA 111, DECEMBER 2014 13