96 THE UNIVERSE. 



The tsetse infests both banks of the Zambesi, and moves 

 only to a short distance from them ; it catches its victims as 

 they make the passage, and darts upon them with the speed 

 of an arrow. Dr. Livingstone says that at the time he trav- 

 elled in this region these flies sometimes buzzed round his 

 head and those of his fellow-travellers as thick as a swarm 

 of bees. They were often stung all over, as were also their 

 asses, but without either themselves or their beasts of bur- 

 den experiencing any troublesome result. The sting of this 

 blood-sucker being fatal to our domestic animals, the ox, 

 horse, sheep, and dog, in the countries it devastates, the 

 goat and ass make up the sum total of agricultural cattle. 



The victims know their executioner ; and when the hum 

 of one of these flies rings in the ears of the cattle they fly, 

 struck with fright, in every direction. 



Such pests as these not only paralyze agriculture, but 

 place a limit to the explorations of man. Deprived of his 

 beasts of burden and his food, he cannot pass through the 

 country of the redoubtable fly ; and if, by chance, he can 

 brave the danger, it is only by taking advantage of the 

 time of its repose. Whenever one is obliged to send flocks 

 of sheep or herds of cattle across countries infested by the 

 tsetse, the natives choose cold moonlight nights, knowing 

 that at such times the insect, sunk in sleep, will not sting 

 the cattle. 



The domestic fly, inoffensive in our dwellings, torments 

 without ceasing those who travel in hot countries. There 

 it is dreaded more than the hyaena and jackal, and we can 

 only guard against it by having a crowd of slaves about us. 

 In some of the villages of Upper Egypt I have sometimes 



