Effect of some environmental factors on survival of overwintering mosquitoes, Culex pipiens pallens.

Abstract

In connection with the possible overwintering of Japanese B encephalitis virus in mosquitoes, some experiments were carried out to examine the effect of temperature, day-length and blood feeding on the survival of the overwintering population of the mosquito, Culex pipiens pallens. No significant difference was observed in the survival rate between the blood-fed and unfed groups under a higher temperature (24 degrees C) and longer day-length (L:D 14:10). Under a lower temperature (16 degrees C) and shorter day-length (L:D 10:14), blood-fed mosquitoes survived twice as long as those under a higher temperature and longer day-length condition. Based on the analysis of wing-length distribution, it was clarified that the blood-fed mosquitoes were a uniform longer-winged group and that most of the shorter-winged mosquitoes were included in the unfed group. Judging from such lower blood-feeding activity of the shorter-winged mosquitoes, their survival rate is suggested to be low during or after overwintering.