TSETSE-FLIES AND COLONISATION 213 



claspers are dilated distally and fused together in the middle 

 line. A description of these appendages, together with 

 photographic illustrations, was given at the lecture ; but as 

 the prints cannot, for various reasons, be reproduced, further 

 details need not be given, as it is difficult to visuahse from 

 descriptions alone. 



The chief breeding-places are, broadly speaking, shady 

 spots in the forest or along the shores of lakes and rivers. A 

 favourite haunt of the pregnant fly is the under-surface of a 

 fallen tree-trunk, or stout branch, which respectively are so 

 placed that they do not quite reach the earth. Beneath the 

 shadow of these the parent fly gives birth to a single larva 

 or maggot, and the newly born creature immediately buries 

 itself in the soil beneath. In such places large numbers of 

 pupae are sometimes found, clearly the offspring of many 

 difierent individuals, but whether the matrons congregate 

 for this pmpose is not clear ; such a trait is, however, common 

 in the house-fly, and numbers of the latter, varying from half- 

 a-dozen to thirty or forty, may be seen laying their eggs in 

 a given spot which could be easily covered by the palm of the 

 hand. Such places as I have indicated are the common 

 breeding haunts of Glossina morsitans and G. palpalis. But 

 the pupae of tsetse-flies have also been found in various other 

 places ; in rot-holes, and between the great buttressed roots 

 of trees ; in the ground under the petioles of palm leaves ; 

 in the burrows of the great ant-bear, and in various other 

 places. 



The duration of the pupal stage may be given as three 

 weeks, but much depends on the temperature and humidity. 

 Much longer periods could be given. 



Tsetse-flies, although very widely distributed over Africa, 

 may be generally locaUsed and confined more or less to " belts " 

 or " zones." Glossina palpalis is met with most abundantly 

 along the banks of rivers and the fringes of the great lakes ; 

 on the other hand, G. morsitans often occurs in suitable places 

 quite remote from water. In parts of Nyasaland with which 

 I am familiar G. morsitans was not found to occur along the 

 banks of the upper reaches of the Shire Eiver, though an 



