Abstract
No age-grading study has hitherto been carried out on A. simpsoni, a known peri-domestic vector of human yellow fever in several parts of Africa. A site in Bwamba where yellow fever had previously been isolated from A. simpsoni was chosen for the present brief study. A parous rate of 56.7% was found, indicative of daily probability of survival of 83 to 87%. All available evidence suggests that A. simpsoni populations in Bwamba are fairly stable, so that similar figures might apply for much of the Year. It is suggested that the shape of the bimodal diurnal biting pattern is not determined by nulliparous and parous A. simpsoni biting at different times of day. The proportions of the 224 A. simpsoni dissected which contained retained ova, microsporidian or Coelomomycesparasites, or previous blood meals are also reported and discussed.