Population Ecology of Culex tarsalis (Diptera: Culicidae) in a Foothill Environment of Kern County, California: Temporal Changes in Female Relative Abundance, Reproductive Status, and Survivorship

Abstract

Temporal variations in the relative abundance and reproductive status of a female Culex tarsalis Coquillett population were studied in the arid Sierra Nevada foothills of Kern County, Calif., during the spring, summer, and fall of 1981. Relative abundance patterns in light and CO₂ traps and in red box shelters were correlated positively throughout and covaried positively with temperature and C. tarsalis abundance in light traps operated at 22 other sites in rural Kern County. The proportions of empty, virgin, and nulliparous females remained relatively constant from May through late August, after which the proportions of empty and virgin females increased markedly. During autumn the population bifurcated into reproductively inactive (presumably overwintering) and reproductively active components. Release-recapture and laboratory observations indicated that during summer the average duration of the nulliparous period was 6 days and the duration of the gonotrophic cycle was 4 days. Daily survivorship of resting females during May–August was estimated vertically to be 0.74 and 0.87 using two calculation methods. The relationship of these estimates to arbovirus transmission is discussed.