266 SCIENCE IN AFRICA 



slaughter of locusts are out of all proportion to the sums spent on 

 research. Such measures can never prove really effective since 

 agricultural country, where locusts can be reached by bands of 

 natives, adjoins much wider areas where the insects can feed and 

 breed at peace. In settled territories extensive control operations 

 have sometimes been organized by governments as a response to 

 public feeling that something ought to be done rather than in a 

 belief in the efficacy of the methods. No more than some measure 

 of defence for standing crops can be expected from these attempts 

 to control widespread invasion. 



Therefore, the efforts towards a successful solution of the locust 

 problem are at present concentrated on the discovery of the 'out- 

 break centres', where the transformation of the harmless solitary 

 locusts into the swarming phase can occur. The results of the 

 international investigations in this respect are most encouraging. 

 Indeed, it has been definitely found that the invasions of the 

 migratory locust can arise only from a single restricted area on 

 the Middle Niger; that the swarms of the red locust originate 

 from two or three areas in Tanganyika and Northern Rhodesia 

 which have been defined; and that the desert locust can trans- 

 form into the gregarious phase only in certain parts of the Red 

 Sea coasts. In contrast to the relative inaccessibility of the out- 

 break centres of the above-named species, the brown locust of 

 South Africa breeds permanently in the comparatively well-known 

 region of the Karroo. 



. The conditions leading to the transformation of phases in the 

 field have also been elucidated to a great extent, so that it appears 

 already possible to embark on the next stage of the problem, viz. 

 the establishment of permanent organizations for the regular 

 supervision of all known and suspected outbreak areas, with a view 

 to suppressing incipient outbreaks as soon as any signs of phase 

 transformation are observed. There is every reason to think that 

 in this way it may be possible to prevent the appearance of the 

 swarming phase and the invasions of wide regions by its swarms. 

 The costs of such permanent preventive organizations are estimated 

 at only a small fraction of the expenditure required to combat 

 swarms when they spread, and they should be regarded as insur- 

 ance premiums against incalculable losses. The difficulties of 



