ENTOMOLOGY 27 1 



tsetse department includes few of the ecological discoveries on 

 which their methods are based. Fly ecology is being studied inten- 

 sively by a research staff, consisting of three entomologists, a general 

 zoologist and a botanist, and includes researches on the species of 

 principal importance in the territory — Glossina morsitans, G. swyn- 

 nertoni, G. pallidipes, G. austeni, and G. palpalis. The subjects of 

 research fall roughly into three categories: i. Association of tsetse 

 with physical and biological complexes of the environment: rela- 

 tions with man, animals, plant communities; the effects of seasonal 

 change, parasites, predators, and fire. 2. Experimental alteration 

 of physical and biological environment: by firing grass and bush, 

 altering plant succession, altering the animal population qualita- 

 tively and quantitatively. 3. Biological control: nothing of real 

 value is yet known, though two parasites have been tried, one of 

 them exhaustively. 



In Southern Rhodesia the main tsetse fly problem is created 

 by the tendency of G. morsitans, which disappeared from the vast 

 tracts of country after the rinderpest epizootic in 1896, to spread 

 from the small areas where it survived. Portions of the country 

 from which the fly receded have been occupied by European 

 agriculturalists and in most of this potential fly area natives have 

 acquired cattle. Whilst the natives in these areas have mostly 

 lived in fly country for generations, and suffer the loss of the cattle 

 they have acquired without exhibiting any desire to leave their 

 ancestral homes, European settlement is inevitably driven back 

 before the encroaching fly. Contact between fly and European 

 settlements was first established in 191 8, since when some farms 

 have been evacuated and a great many more have been threatened 

 with disaster. To give some idea of the rate of fly encroachment, 

 at one time it was estimated that the pest was adding about 1,000 

 square miles to its territory annually. 



The country actually infested with tsetse at the present time 

 lies mostly at low altitudes and includes the Zambesi valley. For 

 reasons of climate and of its poor fertility, this land is unfitted for 

 European occupation, and is capable of supporting only a small 

 and scattered native population. Only small areas are worth 

 heavy expenditure, and at present there is insufficient pressure of 

 population, either European or native, to make urgent the recia- 



