A STEPWISE COMPUTER PROGRAM FOR ESTIMATING DEVELOPMENT TIME AND SURVIVAL OF AEDES VEXANS (DIPTERA: CULICIDAE) LARVAE AND PUPAE IN FIELD POPULATIONS IN SOUTHERN ALBERTA

Publisher Website
Google Scholar
Abstract
Growth and survival rates for larvae and pupae of Aedes vexans (Meigen) were measured in the laboratory at constant temperatures of 10°, 15°, 20°, 25°, and 30 °C. Growth rates in all stages increased with temperature except for 1st stage larvae which developed marginally faster at 25°C than at 30°C. The shortest stage at all temperatures was the 2nd, followed in most cases by the 3rd, 1st, and 4th larval stages, and then pupae; pupae and 4th stage larvae took markedly longer to develop at low temperatures. Average survival rate was about 99% every 3 h for larvae and 98% for pupae. At 10° and 15°C, 1st and 2nd stage larvae survived no better than later stages, but at the higher temperatures survival to the 3rd stage larva was better than 90% but decreased markedly in the 3rd and 4th stages. Overall survival was highest at 25°C. Mosquitoes reared at 10°C did not pupate, while those reared at 30 °C pupated but adults did not emerge.These laboratory data were used in a computer program whose output under field temperature regimes was compared with events in the field. The program works in 3 h time-steps. Rate of development varies with temperature and utilizes a modification of the algorithm of Stinner et al. (1975); the modification removes time as the independent variable in the development equation. Mortality rates are constant at 1% every 3 h for larvae and 2% for pupae. The program’s predictions for graduation from one stage to the next in the field population were all within about 13 h of the observed times and at the start of the pupal stage after 400 h, the output was running 13 h slow. The program appears to run slow at median temperatures below 10 °C and fast at median temperatures above 14°C. Events in the laboratory rearings are offered as possible explanations for these discrepancies. Predicted population size was close to that observed until the late 4th stage larva, from which point it deviated markedly. Pupal mortality in the field was much higher than in the laboratory.