CHAPTER I. 



GENERAL CHARACTERS OF TSETSE-FLIES. 



GEOGRAPHICAL DISTRIBUTION OF TSETSE-FLIES IN GENERAL. 



THE CLASSIFICATION OF TSETSE-FLIES. 



The species of the genus Glossina are dark brown, blackish, yellowish- 

 brown, or yellowish flies, ranging in length (excluding the proboscis 

 and wings) from about 6 or 8 mm. in the case of G. tachinoides, to as 

 much as 13 or 13 -5 mm. in that of G. brevipalpis or G. longipennis. 

 In all species there is a prominent proboscis ; the abdomen in the 

 G. morsitans Group and in G. tachinoides is of a paler colour and marked 

 with sharply denned dark brown bands, interrupted in the middle 

 line, but this part of the body is invisible when the insect is at rest, 

 since it is then concealed beneath the wings (Austen). 



The blood-sucking habit in Tsetse-flies is common to both sexes. 1 

 " The sexes of Tsetse-flies can readily be distinguished when specimens 

 can be examined, since in the male the external genitalia form a con- 

 spicuous knob-like protuberance (hypopygium) beneath the end of 

 the abdomen, which is absent in the female." (Austen.) 



How to Distinguish Tsetse from other Flies. 



^ It is probable that only those who have suffered from the attacks 

 -of Tsetse-flies can recognise them when on the wing, but in the resting 

 position their identification is easy. In this attitude they can be 



Fig. 1. A Tsetse-fly, Glossina longipennis, Corti (Somaliland), in resting: 

 attitude, showing the position of the wings. (Partly diagrammatic, x 3. Aften 

 Austen. Reproduced by permission of the Trustees of the British Museum.) 



1 In most other phlebotomic Diptera the females alone suck blood, while 

 the males are harmless. 



