EXPERIMENTAL OBSERVATIONS GOVERNING THE CHOICE OF A TEST METHOD FOR DETERMINING THE DDT-IRRITABILITY OF ADULT MOSQUITOS.

In an attempt to determine the optimum test conditions for assessing the irritability of adult mosquitos to DDT, the author has carried out a series of experiments with two strains of Aedes aegypti, one resistant and one susceptible to DDT. In these experiments a comparison was made between, on the one hand, the results obtained with the three possible test steps included in a tentative method proposed in 1960 by the WHO Expert Committee on Insecticides, and, on the other hand, the results with those same steps to which modifications proposed by M. Coluzzi were applied.The conclusions drawn from these investigations are that Alternative Step B of the WHO Expert Committee method is the best test step, and that the optimum conditions for performance of this technique are provided by a combination of elements from both the WHO Expert Committee and the Coluzzi methods (2% DDT test papers, three-minute settling period, Coluzzi illumination). This is in fact the technique recommended as standard in 1963 by the WHO Expert Committee on Insecticides.