i6o AFRICAN NATURE NOTES chap. 



southern bank of the Zambesi to the Falls, they 

 were unaware of this sudden increase in the numbers 

 of the tse-tse flies. 



I am still quite unable to account for the sudden 

 and rapid increase in the number of tse-tse flies 

 aloncr the waggon track between Leshuma and 

 Kazuno-ula between August and November 1888, 

 as it is quite certain that up to the latter month 

 they had taken no toll of blood from the cattle 

 which had been driven backwards and forwards 

 along the road either by night or during the cold 

 weather in June or July. 



I knew that my friend the late Dr. Bradshaw 

 used to hold the view that the tse-tse fly deposited 

 its eggs in buffalo dung, and I thought at the 

 time that the cattle dung had been taken as a 

 substitute. The very important researches, however, 

 of Lieutenant-Colonel Bruce in Zululand have shown 

 that '"the 'tse-tse fly does not lay eggs as do the majority 

 of the Diptera, but extrudes a yellow coloured laTva, 

 nearly as large as the abdomen of the mot her.'' The 

 perfect insect does not hatch out for six weeks, so that 

 the increase by generation from a small number of 

 individuals in the course of a few months would not 

 be very great. I can only think, therefore, that all 

 the tse-tse flies throughout the bush through which 

 the ten miles of road led from Leshuma to the Chobi 

 must have been attracted to its neighbourhood by 

 the smell of the cattle dung, which no doubt they 

 mistook for that of buffaloes, the animals with which 

 they have always been so closely associated in the 

 countries to the south of the Zambesi. I am, 

 however, not at all satisfied with this explanation. 



I was obliged to keep my waggon standing on 

 the bank of the Zambesi (waiting for ivory to be 

 brought down from the Barotse valley) until late in 

 November 1888, so that when I was at last able to 

 send my oxen down to the river to bring it through 



