STUDIES ON THE KINETIC RESPONSE OF MOSQUITOS TO CHEMICALS.

An apparatus is described for study of the activity of mosquitos either with or without stimulation by exposure to insecticides or other chemicals such as repellents. Batches of up to 30 mosquitos can be used and they can be studied for a longer time than is possible with, for instance, the method put forward in 1960 by the WHO Expert Committee on Insecticides. Random activity by the test insects, in the absence of directional stimuli due to light or chemicals, is converted to progress through baffles in the partitions separating a series of four boxes and is expressed as a percentage of the total possible activity that would be shown if all the insects passed all the baffles. Exposure to chemicals, by exposure to impregnated papers, can take place before the mosquitos are put in the apparatus, or in the first box. In the experiments described, the activity of recently fed female Anopheles was studied over periods of up to 20 hours.Comparison of the method described with other methods shows that it shares the high variance characteristic of all current procedures for studying mosquito behaviour, although the use of large numbers of insects over long periods has some advantages. The method does, however, give information on mortality under conditions of facultative contact that may be a valuable supplement to the results of conventional susceptibility tests.