Photo below taken by Jason Williams
Plate and some information from Mosquitoes of North America by Stanley Carpenter and Walter LaCasse
Culex tarsalis
Medium-size species
Proboscis: Dark-scaled, with a broad median white band
Palpi: Short, dark with a few white scales at tip and at apex of third segment
Head: Occiput with narrow white scales in a median triangular patch, broad posteriorly, narrow anteriorly; Eyes margined with narrow white scales ; erect forked scales on dorsal surface dark, a few pale ones on the median area; a submedian patch of narrow golden-brown scales behind the eye margin; broad white scales on lateral region of occiput.
Thorax: Integument of scutum dark brown to black; scutum clothed with fine narrow curved golden-brown scales dorsally, narrowly margined anteriorly and laterally with narrow white scales. Prescutellar space with white scales ; a pair of narrow submedian white lines extending forward to near middle of scutum and each terminating in a small white submedian spot which is often separated from the white line by brown scales. Scutellum with narrow whitish scales and brown setae on the lobes. Pleura with small patches of broad dingy-white scales.
Abdomen: First tergite with a median patch of dark bronze-brown scales, may have few pale ones intermixed; Second tergite dark-scaled , with a median basal triangular patch of pale scales; Remaining tergites dark, with prominent basal bands of white or yellowish-white scales; The terminal segments often with apical scaling as well as basal, the eighth segment often entirely pale-scaled. Venter pale-scaled, with a V-shaped marking of dark scales on each sternite, the base of the V at the median anterior margin.
Legs: Hind legs dark-scaled except for the following markings: posterior surface of femora and tibiae mostly yellowish-white-scaled; a narrow line of white scales or a row of spots on anterior surface of femora, tibiae, and often first segment of tarsi; femora and tibiae tipped apically with white ; wide basal and apical white bands on tarsal segments. Front and middle legs similarly marked but with tarsal bands narrower on segments 1-3, reduced or absent on segments 4 and 5.
Wing: Length about 4.0 to 4.4 mm. Scales narrow, dark, a few white scales on costa and subcosta.
Distribution: The western, central, and southern United States and southwestern Canada and down to Mexico.
Bionomics: Larvae found in clear or foul water in a variety of habitats including ditches, irrigation systems, ground pools, marshes, pools in stream beds, rain barrels, hoofprints, and ornamental pools. Foul water in corrals and around slaughter yards appear to be favorite habitats in many localities. Species has been found to 9,000 feetin the Rockies in Utah. Larval production commences during late spring and continues until early autumn. Several generations produced each year with maximum adult population reached during August or September. Females are painful and persistent biters, attacking at dusk and after dark, and readily entering dwellings for blood meals. Domestic and wild birds seem to be the preferred hosts, and man, cows, and horses are generally incidental hosts. The adults hide in sheltered places during the day. Adult females pass the winter in colder climates in hibernation in basements, cellars, caves, and outbuildings where protection from cold. Flight range ...1 to 2 miles.
Medical Importance: Culex tarsalis is the chief vector of Western Equine Encephalitis, also vector of St. Louis and California encephalitis, and now is the main vector of West Nile Virus in the Western States.