Overwintering Studies on Culex tarsalis (Diptera: Culicidae) in Kern County, California: Temporal Changes in Abundance and Reproductive Status with Comparative Observations on C. quinquefasciatus (Diptera: Culicidae)

Population ecology of Culex tarsalis Coquillett was studied at Hart Park, Kern County, Calif., during the winters of 1982-83 and 1983-84. Female relative abundance declined during autumn to a minimum in December and January. Most females collected during winter were empty, inseminated, and nulliparous, indicating a cessation of gonotrophic activity. However, observations on ovarian morphometry indicated that the hibernating states achieved included reproductive diapause, quiescence, and perhaps oligopause. Females remained vagile and readily repopulated resting sites after removal sampling. Relative abundance increased in late February and March in association with the renewal of gonotrophic activity, but before the emergence of the progeny of overwintering females. Overwintering arboviruses were not isolated from 1,176 C. tarsalis females collected from November 1983 to March 1984. Observations on ovarian dynamics of concurrently collected C. quinquefasciatus indicated that the hibernating states achieved were comparable with those observed for C. tarsalis. Relative abundance declined throughout winter and did not recover coincidentally with the renewal of gonotrophic activity in March.