INTRODUCTION. 



The insects described and illustrated in the following pages are 

 of vital importance to the prosperity and future development of 

 Tropical Africa. Until quite lately it was considered by those 

 best cjualified to form an opinion that Sleeping Sickness is 

 disseminated solely by the species of Tsetse-fly known as Glossina 

 palpalis. The recent occurrence, however, of a number of isolated 

 cases of the disease in the Nyasaland Protectorate and the valley 

 of the Luangwa River, North-Eastern Rhodesia, in both of which 

 localities Glossina palpaJis is believed to be non-existent, has 

 caused grave suspicion to attach to two other species of Tsetse 

 {Glossina morsitans and G. brevipal^fis). Experts have for some 

 time been aware that Nagana or other closely similar trypano- 

 somiases of domestic animals can be conveyed by the bites of 

 several species of Tsetse-flies, including Glossina palpalis, and the 

 possibility that Trypanosoma gamhiense, the parasite of human 

 trypanosomiasis, or Sleeping Sickness, may have more than one 

 insect vector naturally suggested itself ; yet, until the alarming 

 discovery of the cases referred to, the results of observation 

 appeared to negative any such conclusion. Whether, as certain 

 authorities believe, the Rhodesian parasite is specifically distinct 

 from Trypanosoma gamhiense or not, it is here only necessary to 

 point out that should such a differentiation in the actual causative 

 agent of the disease be established, the probability that more 

 than one species of Glossina is acting as a carrier would thereby 

 be increased. In any case, it is obviously desirable that Colonial 

 Medical Officers and other officials in Tropical Africa should have 

 a ready means of recognising and accurately identifying the 

 Tsetse-flies found in their districts, and it is hoped that the 

 prfeent volume may serve as a means to this end. 



In the eight years that have elapsed since the publication of 

 the author's " Monograph of the Tsetse-Flies" our knowledge of 

 these insects, thanks to the researches of Sir David Bruce and 

 his collaborators, Professors Minchin and ISTewstead, Dr. J. L. 

 Todd, the late Dr. Koch, Drs. Stuhlmann and Kleine, Mons. E 

 Roubaud, and others, has enormously increased. The Monograph, 

 which is now out of print, contained descriptions and illustrations 



B 



