546 



FAMILY: TRYPANOSOMIDiE 



very closely that of T. gambiense in G. palpalis as described above (Figs. 217 

 and 223). There is an intestinal phase followed by migration forwards of 

 long thin trypanosomes to the proventriculus, labial cavity, and hypo- 

 pharynx, and finally to the salivary gland, where, after the production of 

 free and attached crithidia forms, the infective metacyclic trypanosomes 

 arise (Fig. 226). The characters of the developmental forms as described 

 by Lloyd and Johnson (1924) have been referred to above (p. 515). They 



Fig. 226.— Developmental Form of Trypanosoma brucei in Glossina tachinoides 

 (x 2,000). (After Lloyd and Johnson, 1924.) 



1-3. Forms in mid-gut. 



5-G. Crithidia forms from salivary glands. 



4. Form in proventriculus. 

 7-8. Infective forms from salivary glands. 



are so similar to the developmental forms of T. gambiense that it is 

 impossible to differentiate the two trypanosomes as they occur in the fly. 

 Lloyd and Johnson give the dimensions in microns of the infective forms 

 as they occur in the salivary glands of G. tachinoides as follows: 



Average Length. 



Average Length 

 of Flagellum. 



Average Breadth 

 at Nucleus. 



T. brucei . , 

 T. gambiense 



15-8 (13-3-18-0) 

 14-6 (12-1-17-3) 



2-1 (M-3-5) 

 1-7 (0-5-2-8) 



2-2 (1-4-3-0) 

 1-5 (1-0-2-5) 



Reservoir Hosts.— In his investigations in Zululand, Bruce (1895) 

 found that the wild G. morsitans readily infected dogs and other animals. 

 As there were no domestic animals alive in the district, it was evident that 



