POPULATION-DYNAMICS OF ADULT CULEX MOSQUITOS (DIPTERA, CULICIDAE) ALONG THE KERN RIVER, KERN-COUNTY, CALIFORNIA, IN 1990

The temporal and spatial abundance, dispersal, survivorship, and density of Culex tarsalis Coquillett and Cx. quinquefasciatus Say populations were studied in riparian, agricultural, and residential habitats along the Kern River bed during the drought year of 1990. The temporal abundance of both species was related to cotton agricultural practices and peaked during intensive irrigation after cultivation was terminated in july. Cx. tarsalis peaked in abundance 2 wk earlier than Cx. quinquefasciatus, perhaps because of the advantage of autogenous oviposition, which shortened generation time. Although host-seeking females of both species were most abundant in the riparian habitat, more Cx. quinquefasciatus than Cx. tarsalis were collected in the residential habitat. Marked females released within the riparian habitat were recaptured most frequently within 1 km of the release point; however, flights as far as 12.6 km were documented within the 180-km2 study area. On average, marked Cx. quinquefasciatus dispersed farther and more rapidly than Cx. tarsalis and were recaptured more frequently within the residential habitat. Survivorship, estimated horizontally from the female recapture rate, ranged from 0.60 in May to 0.79 in July for Cx. tarsalis and from 0.74 in September to 0.84 in July for Cx. quinquefasciatus. The estimation of survivorship vertically from the parity rate was complicated by elevated autogeny rates in Cx. tarsalis and by the low parity rate in Cx. quinquefasciatus. Cx. tarsalis population density ranged from 125 females per km2 in May to 65,500 per km2 in August, and was well correlated with relative abundance. Collectively, these ecological data indicated that Cx. tarsalis may be important in disseminating arboviruses within the riparian habitat, but that Cx. quinquefasciatus may be important secondarily by disseminating virus from the riparian habitat to the adjacent residential habitat.