even large numbers of any one species of predator reduced, but by no means eliminated, mosquito breeding in numerous pools at Palmalmal. Nevertheless, mosquitoes were never abundant, if present at all, in permanent pools which contained stable associations of several kinds of aquatic predators.

As was proved on many malarious islands during the recent war in the Pacific, an area of reasonable size can be rendered free from malaria by an intensive control programme. Such an anti-malaria campaign involves control of both the Plasmodium in the human being and of the anopheline vector of the Plasmodium. The first of these requirements is accomplished by treatment or removal of gametocyte carriers in the local population, and by suppressive therapy involving the use of such drugs as atebrine; the second, by measures directed against the adult and developmental stages of Anopheles.

One of the most generally useful mosquito-control measures is the treatment of such breeding places as it is impracticable to drain or fill, with various larvicides. During the later war years D.D.T. (dichloro-diphenyl-trichloro-ethane) largely replaced other chemicals used as larvicides.

In such a campaign, all pools suitable for the development of Anopheles should, of course, be subjected to full control if sufficient personnel and materiel are available for control to be maintained efficiently. Where a control project involves the protection of only a small number of men—such as the staff of a radar post or coast-watching station—labour and materials will very likely be in short supply. It might be possible in the initial stages of occupation of such a post to spray every anopheline breeding place within what is considered a safe radius with a D.D.T.-base larvicide. Now, although the wholesale application of D.D.T. to breeding places affords an excellent means of controlling mosquitoes, it must be borne in mind that not only mosquito larvae but their predators as well will be killed. If it proves impossible to maintain larvicidal treatments on a weekly basis, due to a drawing-in of the control perimeter, or a shortage of personnel or materiel, mosquito breeding will recommence; and permanent pools which had previously harboured a minimal number of mosquitoes because they contained a stable predacious macrofauna, will become major centres of mosquito breeding. Such pools would have served as reservoirs for mosquito enemies, and the number of anophelines developing in them would have been insignificant, if they had not been treated with D.D.T. in the first place.

It is suggested that before the commencement of a mosquito-control project an entomological-survey team should enumerate those permanent pools where the presence of aquatic predators keeps the breeding of Culicidae down to a low minimum. These pools should not be sprayed with D.D.T. unless there is a definite assurance that regular control can be maintained. This suggestion applies only to small camps of a temporary nature. Full anopheline control should, of course, be maintained within a sufficient radius of all permanent camps and airfields in malarious zones, without reference to the predacious macrofauna of the breeding places concerned.