284 OUR INSECT FRIENDS AND FOES 



and from which hundreds of horses, cattle, and 

 other animals perish annually, is caused by the 

 Trypanosoma brucei. This disease is transmitted 

 from an infected animal to a healthy one, by 

 several blood-sucking flies, closely related to the 

 Glossina palpalis, and which are popularly known 

 as Tsetse-flies, which is the native name repre- 

 senting the buzzing noise made by these flies. 

 Slightly larger than the common House-fly, these 

 Tsetse-flies are rather handsome insects, very 

 alert during the heat of the day, and very blood- 

 thirsty. Cattle and horses, mules, and other 

 animals become infected after passing through a 

 " fly belt," that is, a track of country where these 

 blood-sucking flies breed and abound. The 

 trypanosomes causing Ngana have been found 

 in the Kudu, Bushbuck, Wildebeest, etc., and 

 although infected the wild game are apparently 

 quite healthy. Unfortunately, therefore, they act 

 as natural reservoirs from which the Tsetse-flies 

 draw the parasites, for the flies transmit the 

 trypanosomes from the wild game to the domestic 

 cattle. Cattle suffering from a chronic form of 

 the disease also serve to give a constant supply 

 of the parasite, the Tsetse-fly first sucking the 

 blood of an infected animal and then alighting 

 upon and biting a healthy one. 



The Trypanosoma evansi, which is the cause 

 of Surra and its varieties, a very widely distri- 

 buted disease prevalent in India, Burma, Indo- 

 China, Java, the Philippines, Mauritius, and 

 North Africa, attacking horses, mules, camels, 

 and, in a slightly less degree, cattle, is transmitted 

 by various species of Tabanus flies, more 



