This is a large genus of mosquitoes with at least 30 species in North America north of Mexico and over a thousand species worldwide. These two species are two of the most common mosquitoes in urban areas in the U.S. They also are two of the species most implicated in the spread of West Nile Virus as well as some other forms of encephalitis. The adults are nocturnal and the female deposits eggs on many types of water resources, including artificial containers, seasonal water areas, and other standing water such as ponds and marshes. Eggs are laid as a “raft” that contains a great many eggs and which floats on the surface of the water. Complete development from egg to adult may take as little as 7 days.
Very important is elimination of breeding resources in landscape, such as discarded containers on the ground, plant containers, rain gutters, bird baths, etc. Larvae feed on organic matter in contaminated water and do not survive in clean water. Discarded tires are a major breeding site, and these should be removed and recycled or drained of water, including drilling holes in old tires to prevent capture of water. Sites that cannot be drained may be filled or treated with larvicides. The wearing of long sleeves and repellent when active outdoors are important measures to prevent bites. Adult mosquitoes can be minimized with fogging for short-term control or barrier treatments of resting sites for longer term control.