The length of life at various humidities of unfed flies and of flies fed for 1 day and 6 days on diets of meat, sugar and water, sugar and water, meat and water, and water alone, is discussed. The continued feeding of flies on a diet of meat, sugar and water brings about a shortening of their life at all humidities when the flies are starved owing to their increased rate of metabolism. Flies fed on sugar and water are more resistant to humidity than flies fed on meat, sugar and water, and the females are more resistant than the males. Flies fed on meat, sugar and water lose weight more rapidly than flies fed on sugar and water.

High humidity is more favourable for growth of the ovaries than low humidity. Humidity has no effect on oviposition at temperatures of 10–35° C., but at 40° C. low humidity is unfavourable.