The following article has been written from notes of observations and experiments extending over nearly three years—April 1909 to December 1911. Its main object is an attempt to demonstrate that a true conception of the production of Auopheline mosquitos in a definite country or district can only be formed by a large amount of continual work throughout the seasons of the year. At the present time very numerous observations are still to be made before much generalising should be allowed concerning the breeding-grounds and bionomics of these insects.