THE TSETSE PROBLEM IN NORTH MOSSURISE. 317 



by whomsoever carried out, is bound to add usefully to our general knowledge on 

 the subject of controlling tsetse ; (6) because the area cleared of fly was the very area 

 whicli, in the Mossurise district, is best adapted to white settlement. This experi- 

 ment affords a very clear indication that settlement, properly planned, is itself 

 capable of clearing the country settled of the two flies here concerned — G. hrevijpal'pis 

 and G. pallidipes. 



Other points to which I paid particular attention were an analysis of the vege- 

 tation in relation to tsetse, and a study of the distribution and local behaviour 

 of the dangerous and less dangerous woodland types. The practical study of tsetse 

 is, I am convinced, a matter for the botanist and oecologist rather than the unaided 

 entomologist, and this point will be seen to be of the first importance. Each of 

 the tsetses is dependent on particular, but different, shade conditions. Without 

 a clear knowledge (a) of the woodland types that provide these conditions, (6) of 

 those that provide them throughout the year, and (c) of the dry season response 

 of each of these types to elevational and edaphic conditions, exceptional seasons, 

 burning, etc., any clearing operations that may be undertaken in the future for the 

 extirpation of fly, in connection with settlement or otherwise, will be lacking 

 completely in the elements of precision and economy. 



The main practical results have been, I think, the clear defining of the several 

 fly-areas and of the situation at Spungabera, the lessons, both general and in relation 

 to future settlement in Mossurise, to be drawn from the details of Umzila's success, 

 and, in relation to G. brevipalpis in particular, the fact that the annual grass-fires 

 can be made to play an important part by regulation of the time of burning. In 

 primary forest the control of this fly is unfortunately rendered difficult by the 

 presence of the Landolphia vines, which it may not be wished to sacrifice. 



So far as G. morsitans is concerned, it seems to me that the possibility of taking 

 advantage of its highly gregarious and localised habits is worthy of further study. 



I conclude by expressing my very high indebtedness to Snr. Lanne and, in his 

 absence, Snr. A. P. Monteiro for going out of their way to do all in their power to 

 assist me in making a success of the investigation, and to my old friend Snr. Ferreira 

 for his very cordial offer of help on learning that I was working in his district also. 

 I am likewise particularly highly indebted to Dr. W. T. Lawrence of Gogoyo, who 

 not only gave me such information as he already possessed with regard to the fly 

 and continuously collected tsetses for me locally, but also rendered my work east 

 of the Sitatongas and south of the Mtshanedzi possible in this foodless season by 

 lending me native food in considerable quantity. Mrs. Lawrence most kindly 

 presented me with gauze for nets at a moment when it was particularly acceptable, 

 and Messrs. J. W. Scott and G. D. Otterson, living in the mountains, were good 

 enough to assist me in a test of the resistance of G. morsitans to cold in the pupal 

 stage. For some of the literature of the subject, presented to me at different periods 

 in the expressed hope that I would undertake tsetse investigation, I am indebted to 

 my friends Drs. G. A. K. Marshall and A. G. Bagshawe, Directors of the Imperial 

 Bureau of Entomology and the Tropical Diseases Bureau, London, respectively ; 

 and for copies of his own interesting publications, to Mr. R. W. Jack, Rhodesian 

 Government Entomologist. I have also to thank the Rhodesia Museum and Mr 

 F. P. Mennell, of Bulawayo, for the latter's identifications of a rock collection 

 (737) a2 



