a1 East African Virus Research Institute, Entebbe, Uganda.
In an outdoor population of Aëdes (Stegomyia) aegypti (L.), mainly consisting of subsp. formosus (Wlk.), in Uganda, a series of ten 24-hour catches has shown a sharply-defined biting cycle which corresponds closely to an observed diurnal cycle of flight activity. A main peak of activity occurs one or two hours before sunset, and a lesser peak two or three hours after sunrise.
Comparison with recent work in Kenya suggests that, in comparing the behaviour of populations out of doors with those indoors, a distinction must be made between ssp. formosus and the other two forms of A. aegypti, in which no similar cycle has yet been demonstrated.
Ssp. formosus, which is presumed to be the wildest form of A. aegypti, is shown to have a cyclical behaviour very similar to a related forest species. A. africanus (Theo.).