U.S. Environmental Protection Agency


Date of this Version



Public Health Reports (1896-1970), Vol. 62, No. 3 (Jan. 17, 1947), pp. 84-94


U.S. government work


Laboratory cage tests and controlled experiments in houses have clearly demonstrated that residual-spray deposits of DDT are lethal to mosquitoes for considerable periods. Although these tests valuable information on the durability of DDT residual deposits, they did not give information on the mortality of malaria mosquitoes naturally entering treated dwellings in search of a blood meal. In order to secure a lethal dose of DDT from residual deposits, mosquitoes must actually touch the material and be exposed to it for a considerable period. This period has been shown to vary (1), depending on the temperature, age of treatment, density and distribution of the DDT crystals, and the resistance of the individual mosquitoes. Thus, the habits of the mosquitoes in question are of prime importance in determining the likelihood of their being exposed to DDT deposits for a sufficient time to produce death. If, after entering a treated house, mosquitoes spend all or most of their time flying around, or if they proceed directly to a host, feed, and leave immediately, it is obvious that they would not secure a lethal exposure to the DDT. While it has been known for some time that Anopheles quadrimaculatus mosquitoes spend most of their daytime hours resting quietly in dark, damp, cool, quiet places, no detailed information has been noted on their hour-to-hour activities in buildings during the night or on the length of time they rested on walls or ceilings before or after feeding. It was to gain some idea of these activities that the studies herein described were undertaken.