PHONE
800-231-3236 (toll free)
707-285-2200 (office)
707-285-2210 (fax)

ADDRESS
595 Helman Lane
Cotati, California
94931-9736

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Monday through Friday
7:00AM to 3:30PM

4. THE HOUSE MOSQUITO (CULEX PIPIENS)

With 11 species, Culex is the second largest genus of California mosquitoes. Females of this group have short palpi and a blunt, rather than pointed abdomen. Unlike most Ochlerotatus, they tend to have numerous generations in a year. Several hundred eggs are laid packed together in rafts. A female can lay six or seven times in her forty to fifty day life span.

Culex pipiens occurs on every continent except Antarctica and is the most widely distributed mosquito in the world. In North America two races range north (Cx. pipiens pipiens) and south ( Cx. pipiens quinquefasciatus) of 39ºN latitude, about the level of Sacramento. Cx. p. pipiens lives in the milder coastal climate areas, while Cx. p. quinquefasciatus is found in the warmer inland valleys.

Culex pipiens' main host is wild birds, but it also feeds freely on a wide variety of warm-blooded vertebrates, including man. In northern California, it currently plays only a lesser roll as a carrier of human disease, while in southern California and the Gulf Coast region it is a major carrier of Saint Louis encephalitis. It is also the best known carrier of West Nile Virus, a severe encephalitis virus newly arrived in the Americas that is spreading along the eastern seaboard.

Culex pipiens is a serious pest, called the "house mosquito" becaues it commonly develops in small containers around the home. It shows great skill in finding ways to get into the house where it feeds on the occupants at night. It also occurs in containers and sumps on farms and industrial plants, in polluted waters, and will feed out-of-doors at night.

In Marin and Sonoma counties, complaints are most numerous in the late summer and early fall. Coastal communities like Bolinas, Stinson Beach and Bodega Bay are especially plagued by this mosquito. Complaints of being bitten at night while sleeping are sure to refer to Cx. pipiens since it is the only mosquito in this area that bites throughout the night. Locating the breeding sites sometimes takes a group effort and the skills of a detective.

Septic tank sources

Cx. pipiens larvae typically develop best in dirty, stagnant water containing abundant organic matter, in ground pools and natural and man-made containers. Vector technicians often find improperly installed or maintained underground septic tanks producing huge numbers of this species. The mosquitoes gain entrance thorough cracks in the ground, through poorly fitting or unsealed covers, or by the vent pipes made for removal of gases. We recommend that all vents be covered with window screening, preferably aluminum screen, to exclude adults.

A house mosquito feeds on a Hawaiian 'i'iwi bird. Mosquito-borne malaria infections caused the extinction of many Hawaiian native bird species within a few years after Culex pipiens was introduced to the islands. [Photos: NATIONAL GEOGRAPHIC, September 1995]