Larvae prefer clear, fresh seepage water in sunlit or partly shaded pools. Also found in rice fields and roadside ditches with grass. Over winter as adults. Peak biting activities is dusk and dawn. Flight range is up to 10 miles from its breeding site.
Primarily feeds on mammals, will aggressively bite humans when encountered.
Most important vector of Vivax Malaria in California. Also a vector of Myxoma virus of rabbits. St. Louis Encephalitis virus was isolated from a Sacramento population.