Biological variations in Anopheles darlingi and Anopheles gambiae; their effect on practical malaria control in the neotropical region.

A remarkable range of variation has been demonstrated in the biting habits of A. darlingi in South America. At the centre of its area of distribution, the species comprises both anthropo-endophilic and zoo-exophilic individuals, but the anthropophilic tendencies increase progressively towards the periphery of its distributional area. Conditions of travel and migration, imposed by the South American rain forest, have probably favoured the development of a specialized anthropophilic strain on a geographical pattern. There is ample evidence of a similar strain evolution in A. gambiae, but on a more confused pattern. Aëdes aegypti also presents an outstanding example of variation in biting habits.A proper understanding of the extent and significance on anthropophilic and zoophilic tendencies is essential for the proper conduct of malaria control campaigns; for the formulation of long-term policies; and for the proper evaluation of the probabilities of resistance to insecticides.