28 PUPA AND LARVA. 



slight depression is noticeable, representing the mouth of th« 

 larva. When the pupa is viewed from above or below (sea 

 Fig. 7) the lateral tumid lips, into which, as already stated, 

 the last or twelfth segment is produced, are very conspicuous. 

 They are connected by a dorsal and a ventral ridge, and lips and 

 ridges together enclose the above-mentioned pit, the depth of 

 which is from 1^ to 2 millimetres. In this pit can be seen the 

 vestiges of the posterior stigmata of the larva, one on each side 

 at the base of the lateral lip. Under a platyscopic lens, magni- 

 fying about ten diameters, each stigma has the appearance of a 

 minute closed pore, surrounded by a slight elevation (see 

 Fig. 7a). Each lip is covered externally with minute tubercles 

 or granules, and its edge bears four more or less clearly marked 

 grooves or furrows. The anterior margin of the last segment is 

 slightly rugose, with small longitudinal furrows, as shown in 

 Fig. 7. 



The examination of the pupa renders it possible to supplement 

 or amend, in one or two respects, Colonel Bruce's description of 

 the larva. According to Bruce the latter consists of ten seg- 

 ments, but the examination of the pupa shows that in reality it 

 is composed of twelve. In a specimen which is practically a 

 dried larva, since pupation is evidently not complete, there are 

 strongly marked depressions between the segments producing a 

 conspicuously annulated appearance, which agrees with Bruce's 

 description of the larva. Bruce states that the larva is provided 

 with " two minute spikes " at the end opposite the " black hood"; 

 the latter is represented in the pupa by the deep black twelfth 

 segment, with its prominent lips. The "minute spikes" of the 

 larva would therefore seem to be the mouth-hooks of the ordinary 

 Muscid maggot, which in the Tsetse are perhaps used by the 

 larva to attach itself to the wall of the oviduct of the mother. In 

 Plate I. of Colonel Bruce's " Further Report," the pupa is likewise 

 shown equipped with a similar pair of hooks at the anterior pole. 

 But this must be a mistake ; the pupae before me display no 

 trace of any such structures, and Bruce himself says nothing 

 about them. 



While most other genera of blood-sucking 



D^SbSuon.^ Diptera are practically world-wide in their 



occurrence. Tsetse-flies are confined to Africa, 



and a glance at the accompanying map will show the reader what 



has been learnt of their distribution since Sir William Cornwallis 



Harris [5] encountered Glossina morsifans to the south of the 



