vi INTRODUCTION. 



species of ■wild animals in Africa without doing them any harm, 

 but when taken therefrom and introduced by the proboscis of 

 the Tsetse into the blood of domestic animals multiplies with 

 enormous rapidity, and eventually causes death. Quite recently 

 a similar parasite has been discovered in the blood of man in 

 West Africa, where several species of Tsetse-flies are known to 

 occur. In other parts of the Continent all experience goes to 

 show that the bite of the Tsetse has no ill effect upon man ; 

 and though it is not yet known whether a Tsetse is the means 

 of conveying this new parasite which has been found in human 

 blood, the discovery has at least caused the various West African 

 species to be suspected, and has lent these insects a new 

 importance in the eyes of students of tropical medicine. 



The present work has been prepared with a view not only to 

 supplying a resume of our knowledge of the Tsetse-flies, but also 

 in order to enable those who may be engaged in Africa itself 

 upon the investigation of the maladies produced in different 

 animals by the various species of Trypanosoma, to determine the 

 species of Glossina responsible for the dissemination of the 

 hsematozoon. The systematic portion of the volume has been 

 a matter of considerable difficulty, owing partly to the remark- 

 able dearth in the genus Glossina of structural characters such 

 as might be utilised for the distinction of species, and partly to 

 the faulty condition of the bulk of the material available for 

 examination. Tsetse-flies are generally rare in collections, and 

 so far as regards the number of specimens of these insects in its 

 possession the British Museum would probably compare favour- 

 ably with any other similar institution. But unfortunately 

 most of the material has been collected by sportsmen unprovided 

 with the necessary materials for its preservation, with the result 

 that owing to the rough and ready methods perforce adopted, 

 there are few specimens in our collection that are not more or 

 less damaged. It would not be too much to say that the 

 specimens representing Glossina in the British Museum collection 

 are in poorer condition than those of any other well-known genus 

 of Diptera. In consequence of this, and also of the limited 

 number of specimens from the various localities, no attempt has 

 been made in the systematic portion of this volume to do more 

 than describe the external anatomy of the genus and its 

 different species. The special attention of the reader is, how- 

 ever, directed to Chapter V., in which Dr. H. J. Hansen gives 

 the results of his investigation of the mouth-parts. 



