Temperature and Photoperiod Effects on Larval and Ovarian Development of New Zealand Strains of Culex quinquefasciatus (Diptera: Culicidae)

Effects of temperature and day length on larval and ovarian development and blood-feeding rates of two New Zealand strains of Culex quinquefasciatus Say were studied in the laboratory and compared with those of C. quinquefasciatus of the tropical Fiji Islands and C. pipiens pallens Coquillett of north temperate Japan. Developmental zero (≈°C) and thermal constant for larval plus pupal development (139 degree-days (DD) for male and 150 for female) did not differ among the four strains. First follicles of females reared at 15°C and a photophase of 10 h (hereinafter designated as °C-h) were shorter than those at 28°C-16 h by ≈15% in both New Zealand and Fiji strains. Feeding rates of Fiji females were little influenced by temperature-day length conditions. Feeding rates of New Zealand strains decreased under low temperature-short day length conditions, but ≈30% of females took blood within 1 mo after emergence at 15°C-10 h. In contrast, females from Saga, north temperate Japan, had conspicuously smaller (reduction rate ≈50%) follicles at 15°C-10 h and rarely took blood within 2 mo after emergence. It was concluded that New Zealand strains of C. quinquefasciatus have no distinct ovarian diapause. Southernmost distributions of C. quinquefasciatus reported in the literature correspond well to the July °C isotherm in the Southern Hemisphere, but considerable discrepancies exist between northernmost distributions and the January °C isotherm in the Northern Hemisphere.