Longevity of Aedes aegypti (Diptera: Culicidae) compared in cages and field under ambient conditions in rural Thailand.

Aedes aegypti (L.) were exposed to all of the physiological stresses of a natural environment, without mortality from predation or from the defensive behavior of bitten hosts. Each replicate consisted of four cages containing 50 male and 50 female, locally reared Ae. aegypti. The cages were placed in the bedroom and kitchen of a typical Thai house in the village of Hua Samrong, Chachoengsao Province. Replicates were repeated five times between October 1991 and June 1992. Mosquitoes had constant access to sugar and were offered blood meals every day. The number of dead mosquitoes and eggs were recorded daily for 30 days. Indoor maximum temperatures were high throughout the year, ranging from a mean of 32.8 degrees C in October/November to 37.6 degrees C in March-April, with an absolute maximum of 41 degrees C. Survival in cages was related to temperature, with the force of mortality lowest in November-December (0.002) and highest in May-June (0.043). The negative slope of cohort survival was also greatest in the warmest months. Egg laying rate was lower in the cooler months (minimum 16.4 eggs/female/day in November-December), but did not vary greatly in absolute value (maximum 22.7 eggs/female/day in March-April). Statistically, survival of females in cages was much greater than survival calculated from mark-release-recapture studies conducted by other authors in Hua Samrong. The difference in survival for mosquitoes released in the field and those confined to cages suggests that predation or defensive behavior may be important in regulating adult populations of this vector.