ENTOMOLOGY 269 



in view of the growing importance of soil erosion in Africa, that 

 unless or until the areas reclaimed from tsetse fly can be protected 

 from misuse, reclamation may defeat its own ends. 



The eradication of the flies may be sought through the destruc- 

 tion either of their food supply, or of their habitat. Attempts to 

 starve the flies out of wide areas by wholesale destruction of animals 

 have been tried in several places, as mentioned in Chapter VIII, 

 but, except in Southern Rhodesia, such methods have proved 

 either impossible or undesirable. In Tanganyika experiments and 

 observations have been initiated on the relations of the flies wdth 

 their food-animals, and the conditions under which control of the 

 latter may be necessary. 



Flies can be completely eradicated from any country by clearing 

 the vegetation with the axe, but this method has serious drawbacks: 

 among others, its employment on a large scale is prohibitively 

 expensive. Nevertheless, remarkable results have been achieved, 

 especially in the Shinyanga district of Tanganyika, where the 

 natives have been induced to reclaim their land by voluntary 

 labour. For the past nine years thousands of natives have turned 

 out annually for a fortnight's clearing work, with the result that 

 large areas have been reclaimed. Up to 1933 some 5,000 natives 

 had been able to return to land in one chieftainship from which 

 they had previously been driven by an advance on the part of 

 the flies. Eradication of fly by organized grass fires without 

 clearing the bush, which has been very effective, has limitations, in 

 that continuity of the grass cover must be adequate for suc- 

 cessful burning; but there are said to be many hundreds of 

 square miles in Tanganyika and Southern Uganda suitable for 

 this method of control. Fires are permanently effective only if they 

 can be carried up to and across barriers impassible to fly. Such 

 barriers have been provided in part of Tanganyika by clearing 

 broad bands of vegetation, the country being thereby divided into 

 blocks, in each of which the fly can be attacked with no risk of 

 reinfestation. 



As a subsidiary method of attack, remarkable advances have 

 been made in the wholesale catching of fly by traps. A trap 

 patented by Mr. R. H. Harris has been tried extensively in Zulu- 

 land and now in parts of the Congo; others, devised on a diflferent 



