A total of 10,412 newly emerged imagines of Anopheles culicifacies were released, from May to October, in a large outdoor screened insectary in 16 batches, varying in size from 100 to 1,793, in order to study length of life of this species. The insects were dusted with printers' ink powder of various colours. Climatic and other conditions prevailing inside the insectary were similar to natural conditions outside.
It was found that the maximum longevity of females varied from 8 to 34 days, being longest later in the season when temperature was slightly lower and relative humidity considerably higher. The longest period a male was observed to live was 8 days.
It was also observed that there was always a very rapid falling off in numbers so that at least 50 per cent of imagines released had died by the third day. Reduction in population was by geometric progression. The probable duration of life of A. culicifacies was only two days, and the average life span only four days. But in each batch there were always one or two individuals that were considerably longer lived than the rest.