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A medium-sized mosquito with banded tarsi and a broad crisp white band on the proboscis; wing length 4-4.4 mm.
Proboscis long and dark with a broad white band near the middle. Palps white-tipped. Pedicels with a patch of white scales on median surface. Scutum covered with narrow brown scales, a fine line of white scales extending forward each side of prescutellar space and terminating in a white spot. Abdominal tergites with scattered pale scales on I, a basal triangular patch on II and white basal bands on III-VII. Wing scales dark, a few pale ones near base of C. Legs brown-scaled, hind femur and tibia with a continuous or interrupted row of white scales laterally. White basal and apical bands on all hind and most fore and mid tarsomeres.
Antennae long, dark at base and apex, pale between and strongly spiculate to insertion of 1-A. Head seta 5-C 4 or more branched, 6-C 3 or more branched. 50 or more slipper-shaped comb scales in a patch. Siphon about 5 x 1, pecten on basal third. 5 many-branched setae inserted in line, beyond pecten. Saddle surrounding anal segment. Papillae longer than saddle.
Linnaeus used culex, the Latin word for mosquito when he described the common house mosquito, Culex pipiens. All mosquitoes described in the following 50 years were placed in this genus. In 1818 Meigen decided that there were at least two other major types of mosquito, which he therefore renamed and placed in the genera Anopheles and Aedes. Only three Culex species, one of which is pipiens, are known to occur in British Columbia.
The pale cuticle gives the adults an overall brown colour. The females can readily be separated from those of Anopheles by the short palps and trilobed scutellum, from those of Aedes by the blunt abdomen and from Culiseta and Mansonia females by the absence of both pre- and postspiracular setae.
Eggs are laid in rafts on the surface of almost any standing water.
Larvae have a long narrow respiratory siphon with a short pecten at the base composed of rather small teeth. The siphon lacks basal seta 1-S, but four or more pairs of branched setae arise ventrally beyond the pecten.
Pupae should be kept alive and allowed to emerge.
All our species overwinter as fertilized females and can produce several generations a year.
Cx. tarsalis is common from the coast to the Okanagan and has been taken as far north as Little Fort on the North Thompson and as far east as Cranbrook. It breeds in a variety of water sources such as flooded meadows, open ditches, irrigation seepage, borrow pits and sewage lagoons, and can tolerate a high degree of pollution. Egg rafts are laid in early summer and there are several generations each season. The adults from well fed larvae can mature eggs without a blood meal (Washino & Shad-Del 1969) but normally they take blood from birds, cattle and man, entering houses at night and biting readily. In central Alberta, its preferred hosts are birds, 52%, followed by cattle and man, each 12% (Shemanchuk et al. 1963). Females hibernate in crevices of rock slides, rodent burrows, culverts and cellars. Cx. tarsalis is the principal vector of WEE virus in western Canada (Burton & McLintock 1970) and in the northwestern States (Gjullin & Eddy 1972).
In British Columbia, horses are usually immunized annually against WEE but in regions where the virus occurs (Okanagan and Shuswap Lakes) pesticides will probably be used against both larvae and adults when they and the virus are abundant.
"Culex tarsalis is a native species, widely distributed in ditches and permanent and semipermanent pools in grassland and open woodland in the southern third of the Province. Specimens have recently been found in southern Vancouver Island. It is a proven virus vector, implicated in our human cases of Western Equine Encephalomyelitis (WEE) in the 1970’s. They are present and bite mostly in the early morning and evening all summer. All our Culex and Anopheles species and most Culiseta overwinter as mated females and emerge in early spring for blood meals" (Belton 2007). This species is a competent vector for West Nile Virus (Belton 2007).
Belton, Peter. 2007. British Columbia mosquitoes as vectors of West Nile virus. Peter Belton web site. Simon Fraser University.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2020-07-13 9:13:14 PM]
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