39 8 



coarse teeth and a series of file-like plates. These are 

 capable of being completely everted and consequently, 

 when the proboscis is rotated as a whole, would tear 

 their way through the skin. The proboscis proper 

 consists of three parts (i) the dorsal labrum, (2) the 

 ventral labium, which partly embraces the labrum 

 with a series of inter-locking teeth, and (3) the hypo- 

 pharynx, which lies in a groove in the labium. The 

 hypopharynx has two small lateral appendages, and the 

 tips of the labrum are in apposition with these and 

 keep it in its groove. Owing to the fusion of the 

 labrum in the bulb of the proboscis, no independent 

 longitudinal movements of these parts is possible. 



(Fig. I26A). 



CLASSIFICATION OF SPECIES OF GLOSSINA 



(A) Hind tarsi entirely dark. 



(a) Abdominal segments with sharply defined pale 

 hind borders. Second segment has a conspicuous 

 square or oblong pale area in the centre. 



1. Gl. tachinoides ( = Gl. decorsei). The smallest 

 tsetse fly, 8 mm. excluding proboscis. 3 smaller. In 

 the ? the tarsi are basally somewhat pale. 



(aa) Abdominal segments with hind borders, if 

 lighter, extremely narrow. Second segment has pale 

 area triangular. Larger species than (a). 



2. GL palpalis. Darkest of all species of Glossina. 

 Third joint of antenna dusky-brown to cinereous black. 



2 A. Gl. palpalis, v. wellmani ( = Gl. bocagei). Dis- 

 tinguished from the type by its having the frontal stripe 

 pale ochraceous \ thoracic markings much reduced, so 

 that the thorax In a well-preserved specimen appears 

 spotted, the antero-lateral markings taking the form 

 of spots or blotches ; the spot immediately behind the 



