104 W. A. LAMBORN. 



suggests that a more reasonable explanation is to be found in the local extermination 

 of the flies by their parasites, a process, as he beheves, 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 Hmited 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 hne of action could possibly be found in the search for other species naturally 

 parasitic on Glossina but having a different geographical 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 Mutilhd, 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. 



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 parti- 

 cularly likely to be the case with Mutilhds, 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 parti- 

 cular. They could unquestionably be bred readily enough in the laboratory on the 

 puparia of their natural host, though owing to the difficulty in obtaining these 

 in any numbers, the laboratory output would necessarily be very hmited. It has 

 occurred to the writer that it might be possible to employ as alternative hosts the 

 puparia of some of the common Muscids, then hberating in great numbers the httle 

 insects, each with its dominant aim in Hfe to seek out and destroy the greatest of 

 the insect scourges of man and beast in the African Tropics. 



The general upset of work as a consequence of war conditions made any attempt 

 to put the idea to a practical test impossible, but an opportunity was made to carry 

 out, during 1918 in East Africa and during the last six months of 1919 in Nyasaland, 

 research work in regard to the question of alternative hosts for Chalcids normally 

 parasitic on certain Muscids. The results (which will be written up later) showed 

 some promise, though this work has again, unfortunately, been brought to a prema- 

 ture close. 



