Ill 



elsewhere) which, though suitable for colonisation, are at present 

 paralysed in the absence of animals for transport purposes, cultivation 

 and the other necessities of agriculture and commerce. The abolition 

 of Tsetse-flies would likewise be of especial benefit to the Katanga 

 District of Belgian Congo, where, in consequence of the impossibility 

 of keeping alive the oxen, horses or mules necessary for clearing, 

 ploughing, weeding and harvesting, settlers have been obliged to 

 import machines from Europe at great expense, and to employ skilled 

 white labour to keep them going. 



As yet we know very little with regard to means of limiting and 

 destroying Tsetse-flies, and it is to these points especially that the 

 attention of investigators should be directed, for the discovery of 

 an effective method of campaign against these terrible Diptera would 

 render an immense service to all Tropical African colonies and 

 protectorates. 



The results that have accrued from a precise knowledge of the bio- 

 nomics of mosquitos belonging to the genera Anopheles and Stegomyia, 

 the disseminators of malaria and yellow fever, should not be overlooked. 

 Thus, to quote a single instance, the Americans, by taking effective 

 measures for the destruction of these insects, and especially their 

 aquatic larvae, have succeeded in ridding the Southern States of the 

 Union and the neighbouring island of Cuba from a scourge that was 

 retarding the economic development of some of the most fertile portions 

 of the globe. 



Measures of this kind have also been of great assistance to the 

 American authorities in the sanitation of the Panama Canal Zone. 

 The very low death-rate among the personnel engaged upon the work 

 of construction, and the fact that the gigantic feat represented by the 

 completion of the Canal was performed in a minimum of time, were 

 largely due to the progress made by medical entomology. 1 



In view of the fragmentary nature of the available data, all that 

 can be done here is to indicate possible aids in conducting a campaign 

 against Tsetse-flies. For the sake of convenience these will be dealt 

 with under different headings. 



ENEMIES OF TSETSE-FLIES. Under this heading, before con- 

 sidering species directly hostile to Glossina, it may be of interest 

 to say a word or two as to indirect enemies. These may be cither 

 carnivorous mammals or biting flies belonging to other genera, both 



1 The antimalarial measures taken by the Americans in the Panama Canal 

 Zone, covering 10 miles in breadth and 45 miles in length, entailed the employ- 

 ment of a numerous and highly trained staff. No fewer than a quarter of a 

 million human beings, introduced into this zone during the five years covered 

 by the American occupation, had to be protected against the terrible malarial 

 fever, which had proved so formidable an obstacle to the first attempt at piercing 

 the Isthmus made by the French. 



The measures adopted consisted essentially in : (1) The destruction of 

 Anopheles breeding places to a distance of 100 metres from habitations ; (2) the 

 abolition, over the same area, of all cover for the adult mosquito ; (3) the 

 screening of all openings in dwellings, so as to prevent the entrance of mosquitos ; 

 (4) The application of crude oil, or another larvicide of special composition, 

 to all breeding places which it was impossible to drain, in order to destroy the 

 larvae. 



This procedure was based on the facts that Anopheline larvae are accustomed 

 to live in fresh, clear water, containing an abundance of algae and other vegetation, 

 and that the adult mosquito is not supposed to travel far, and needs herbage 

 and bushes in which to shelter from the wind. 



