The responses of anopheline vector populations to malaria-control operations were studied. Most of the emphasis was placed on their response to DDT, dieldrin, and lindane residual house spraying and on their implication for malaria control and eradication programs. The investigation deals mainly with Anopheles labranchiae Falleroni, A. sergentii (Theobald), A. stephensi Liston, A. funestus Giles, A. gambiae Giles, s.l., A. pseudopunctipennis Theobald, A. albimanus Wiedemann, A. darlingi Root, A. nunestovari Gabaldon, A. aquasalis Curry, A. culicifacies Giles, A. m. minimus Theobald, A. m. flavirostris (Ludlow), A. maculatus Theobald, A. sundaicus (Rodenwaldt), A. b. balabacensis Baisas, A. leucosphyrus Dönitz, and the A. punctulatus Dönitz group.
The intrinsic vector ecology and behavior are of importance in explaining the response of any vector population to control measures, but the most important clues to this response are the relationships between ecology, behavior, and the environment. Exophilic and exophagic tendencies have no protective value in an insecticide house-sprayed area if there are no available outside shelters or convenient alternative hosts spending the night outside treated premises. In some instances major differences in response to insecticide treatment within a vector species in various areas of its distribution cannot be explained by changes in the environment. This may be attributed to less genetic plasticity of the species in some areas, restricting its adaptability.
It is stated that even where extensive prespraying data on vector ecology and behavior were available, the predictions about the vector population response to treatment have often been misleading, indicating that the investigations may have been incomplete or biased by sampling difficulties.
At times vector control has been surprisingly easy and has led to malaria eradication without difficulty. On the other hand, there have been many continuous control operations which have been unsuccessful in tropical areas. Quite often, a weakness in control operations or a change in the environment allows the vector to resume malaria transmission at the same or higher levels.
