1 66 AFRICAN NATURE NOTES chap. 



its continued existence, certain climatic and other 

 conditions which have never yet been satisfactorily 

 explained have always prevented tse-tse flies from 

 spreading into all parts of the country in which 

 buffaloes were once found. In Southern Africa 

 the tse-tse fly has always been confined to a strip 

 of country along the south-east coast, and the hot, 

 well-wooded valleys of the Zambesi and Limpopo 

 rivers and their tributaries. Apparently the tse- 

 tse fly {Glossina morsitans) requires a certain degree 

 of heat in the atmosphere, or can only stand a 

 certain degree of cold ; for along the east coast 

 it seems never to have existed to the south of St. 

 Lucia Bay, in the 28th parallel of south latitude, 

 although buffaloes were once plentiful far beyond 

 this limit, all through the coast lands of Natal 

 and the Cape Colony, as far as Mossel Bay. Nor 

 are these insects ever found at a high altitude 

 above the sea. ** Fly " country is usually less than 

 3000 feet above sea-level, though in places such 

 as the district to the north of Hartley Hills, in 

 Mashunaland, tse-tse flies ascend to a height of 

 nearly 3500 feet. Nearer the equator, they are 

 able to live at a higher level, and I have myself 

 met with tse - tse flies near the upper Kafukwe 

 river at an altitude of at least 4000 feet above 

 the sea. 



The tse-tse flies spread with the buffaloes from 

 the sea-coast all along the Limpopo to beyond 

 its junction with the Maghaliquain, but were not 

 able to accompany them to higher ground. The 

 buffaloes, however, spread right up to near the 

 sources of the Limpopo and its tributaries, crossed 

 the watershed to the reed beds of the Molopo, 

 and from thence spread through Bechwanaland as 

 far south as the Orange river, hundreds of miles 

 away from the nearest '' fly "-infested area. Even 

 in the midst of low-lying districts full of buffaloes, 



