XVI] REPRODUCTION 247 



The method of reproduction, discovered by Bruce, is very 

 remarkable, resembling that of the Pupipara, and is probably 

 the result of their exclusively blood-sucking mode of life. 

 The female lays a single larva at a time, which is retained and 

 nourished in the oviduct until it is full grown. After the 

 larva is born, it at once burrows into the ground and pupates. 

 The larva is generally of a yellowish-white colour and bears at 

 its posterior extremity a pair of large dark-coloured protu- 

 berances and between them is a depression into which open 

 the spiracles (Fig. 70). The pupa is dark brown in colour 

 with a slight sheen. It is broadly ovoid in shape and the 

 larval protuberances are equally conspicuous, forming, to- 

 gether with the size and shape of the depression between them, 

 a means of identifying the immature stages of different species. 



Distribution. The members of this genus are entirely re- 

 stricted to Africa and the south-west corner of Arabia, together 

 forming the Ethiopian region, and range between the latitudes 

 of 18 N. and about 31 S. Within these limits the tsetse-flies 

 are not found continuously but are generally confined to belts 

 or patches of forests, bush, and warm and damp situations where 

 shade can be obtained. The areas in which the tsetse- fly 

 occurs are commonly known as " fly-belts " and are well 

 exemplified in the case of G. morsitans. Tsetse-flies are said 

 to be absent from dry open plains without shade. 



Determination of the species of GLOSSINA. 



It seems probable that most, if not all, of the species of 

 the genus Glossina, are of importance as carriers of disease 

 and therefore we include the following table for their determina- 

 tion. In the classification, the important work of Austen has 

 been followed throughout, and according to his scheme the 

 species may be divided into four groups : 



