133 



More recent study of the flies has shown that this is not the case, and 

 the writer suggests that a more reasonable explanation is to be found 

 in the local extermination of the flies by their parasites, a process, as 

 he believes, now steadily proceeding in the area near Mzeze, Nyasaland. 

 The question therefore naturally arises how far is it possible to 

 increase their influence either by the introduction of new parasites or 

 by breeding on a larger scale those already known to science ? 



" The genus Glossina being now limited to the Ethiopian region, it 

 is doubtful how far the parasites of other Diptera, brought in from 

 other lands, would seek out and destroy its puparia. It is to be 

 apprehended that those obtained from the puparia of other Muscids, 

 breeding under more or less similar conditions, might do so. A more 

 hopeful line of action could possibly be found in the search for other 

 species naturally parasitic on Glossina but having a different geo- 

 graphical distribution. For instance a Bombyliid fly, Villa lloydi, 

 Austen, parasitic on G. morsitans, has so far only been discovered in 

 Rhodesia, and a second species of parasitic Mutillid, M. benefactrix, 

 Turner, in Nyasaland only. The parasites of the fly on the West Coast 

 are probably different from those in the east and south, the insect 

 fauna, generally speaking, being largely distinct. The various species 

 of tsetse-flies may each have different parasites yet to be discovered, 

 which might be interchangeable. 



a 



Fig. 18. Puparia of Glossina morsitans, showing holes of emergence of: a, the 

 hyperparasite Syntomosphyrum glossinae, Wtst. ; b, tho parasite. Stomatoceras 

 micans,Wtst. (Alter Waters ton, 161). 



"It is probable, and some of the evidence on this point is very 

 definite, that in the case of rapid extension of a fly area, parasites less 

 endowed than their hosts with the power of ranging far and wide- 

 strength on the wing having doubtless played a considerable part in 

 the present-day success of the tsetse as an insect have lagged more 

 or less behind in the foci first inhabited by the flies. And this is 

 particularly likely to be the case with Mutillids, the females of which 

 are wingless. One of the present suggestions in connection with fly 

 control is to endeavour to enhance the value of the parasites already 

 known to science, the Chalcids in particular. They could unquestion- 

 ably be bred readily enough in the laboratory on the puparia of then- 

 natural host, though owing to the difficulty in obtaining these in any 



