PEEFACE. 



G. pallidipes, that the disease owes its prevalence in special 

 localities, and it is apparently these species which Colonel Bruce 

 used in his experiments. 



The question immediately arises as to whether the other 

 species of Glossina are carriers of disease germs ; and whether 

 other species of Trypanosoma, especially that found infesting the 

 human blood and cavitary fluids, ai-e carried by species of 

 Glossina or Tsetse-fly. 



An accurate knowledge of Tsetse-flies is clearly indispensable 

 for further progress in this inquiry. 



Inasmuch as the genus Glossina is found only in Africa, it 

 is certain that in India and in South America other carriers of 

 the Trypanosoma must be at work. At present, though it 

 appears that Stomoxys and some other " biting flies," not scienti- 

 fically determined, have been experimentally shown to be capable 

 of carrying the Trypanosoma of Surra and of Nagana from one 

 animal to another, no constant association of any genus or 

 species of fly with these Trypanosoma-diseases has been sug- 

 gested, excepting that of Glossina with the African Nagana 

 disease. 



In view of the fact that the Trypanosoma parasite is not 

 observed to undergo any developmental changes within the 

 Tsetse-fly similar to the changes which the malaria-parasite 

 Laverania undergoes in the body of the gnats of the genus 

 Anopheles, it is not unreasonable to suppose that there is no 

 such exclusive bond of association between Glossina and Trypa- 

 nosoma as there is between Anopheles and Laverania. Other 

 carriers may serve for Trypanosoma, though Laverania must 

 have Anopheles and no other. 



On these points we require further observation. Collectiona 

 from all parts of the world of flies (and other insects) which suck 

 the blood of human beings and other animals are needed, accom- 

 panied by careful notes as to habits, locality, and life-history. 

 Such collections will be received with special welcome, and at 

 once investigated if addressed to me, here. It is clear that an 

 accurate and comprehensive study of blood-sucking organisms, 

 in view of their possible action as carriers of disease, has become 

 a matter of the most urgent public importance. 



As an illustration of the significance of the discrimination of 

 the difi'erent species of blood-sucking flies, I may mention that 

 whilst these lines are in the press, I have received from Colonel 

 Bruce a small box of biting flies taken at Entebbe, Uganda, 



