292 G. BREVIPALPIS AND DISEASE [CH. 



and slight!}' damp, and the larva will at once burrow beneath 

 the surface." 



The average duration of the pupal stage at 30° C. was found 

 to be about 36 days, but by varying the temperature it could 

 be shortened to 30 days or prolonged to as much as 65 days. 



There is some evidence to shew that this species may 

 reproduce parthenogenetically, for on two occasions Stuhlmann 

 observed fully developed larvae laid by virgin females that had 

 been bred in captivity. 



G. BREVIPALPIS and Disease. 



Although there is little doubt that the present species is 

 an important carrier of cattle trypanosomes precise information 

 is lacking. According to Stuhlmann, in German East Africa 

 it is one of the chief disseminators of Nagana among domestic 

 animals. Both Koch and Stuhlmann fed G. brevipalpis on 

 animals infected with T. brucei and attempted to trace the 

 development of the parasite within the vertebrate host. The 

 latter author gives an interesting description of the various 

 supposed developmiental changes undergone by the trypano- 

 somes, but in no case did any direct inoculation experiments 

 give positive results and therefore the transmission of T. brucei 

 by G. brevipalpis remains as yet unproven. 



Similarly in the case of T. gambiense, Koch observed a 

 commencement of its development in the gut of G. brevipalpis 

 and Fischer is of the opinion that this species may occasionally 

 act as an intermediate host for sleeping sickness. 



Dr P. H. Ross has shewn that the fly is able to transmit 

 mechanically T. gambiense from infected to healthy monkeys. 

 During 91 days, 51 flies were fed first on an infected monkey 

 and eight hours later on a healthy one. The latter shewed 

 parasites in its blood on the ninety-fifth day. 



Later the same investigator had two positive results in the 

 transmission of T. gambiense by G. brevipalpis employing the 

 " interrupted " method of feeding, but as the flies were caught 

 in nature there is a shght doubt as to whether the trypanosome 

 was really gambiense. 



