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SOME NOTES AND REMARKS ON THE BIONOMICS OF GLOSSINA 



MORSITANS. 

 By Rupert W. Jack, F.E.S., 



Agricultural Eyitomologist, S. Rhodesia. 

 It is with considerable diffidence that the writer has prepared the following paper, 

 not only on account of several previous contributions to the subject, but also, and 

 chiefly, because no opportunity has been available for more than comparatively 

 brief visits to the fly areas in Southern Rhodesia, and the observations to be recorded 

 are therefore of a somewhat meagre nature compared with work that has been carried 

 out of recent years in other parts of Africa. The tsetse-fly problem is, however, of 

 such paramount importance to Africa as a whole, and the continued extension of the 

 fly belts such a grave hindrance to the full development of Southern Rhodesia, that 

 it is felt that too much time and thought cannot be devoted to the subject, and that 

 every contribution whether of actual observations or of theoretical deductions, or of 

 both, must have a certain value, if only in provoking discussion and criticism. In 

 the following pages the important question of whether or not Glossina morsitans is 

 vitally dependent upon the larger mammals is not directly dealt with. The strong 

 trend of scientific opinion in the direction of an affirmative conclusion must be 

 admitted at the present day by the most vigorous opponent of the theory. There is 

 hardly an investigator of any standing who has not contributed some observations 

 of weight, indicating that the fly is mainly dependent upon the larger mammals for 

 its food supply. For the purposes of the present discussion this dependence has been 

 to a large extent assumed with a view to an attempt to explain certain phenomena 

 upon this basis. The discussion is, however, of a very disconnected nature and aims 

 merely at touching upon a few points in connection with the bionomics of the fly that 

 need clearing up, and if the writer's views provoke criticism, or even direct con- 

 tradiction, supported by actual observations, the paper will have served its purpose, 

 as our knowledge of the subject cannot fail to benefit thereby. 



It will be found that there is a very substantial agreement between observations 

 in this territory and those recorded further north, particularly in Northern Rhodesia, 

 but there are several important points bearing on the fly problem concerning which 

 a considerable difference of opinion appears to exist, and others that have not 

 apparently been touched upon as yet. 



The points raised include : — (1) the conditions in the dry season in respect to the 

 welfare of the fly ; (2) the effect of grass burning on the numbers of the fly ; (3) the 

 value of mopani country to the fly ; (4) the question of migration under the influence 

 of hunger or other stimulus ; (5) the question of fly moving about infested areas with 

 game ; (6) the distance at which the fly can detect its hosts ; (7) the following 

 distance of female flies. 



In the following pages it is desired to emphasise the importance of these points, 

 stating the writer's own attitude of mind towards them in the hght of available 

 evidence, but without preferring any claim to having reached a final conclusion. 

 Direct investigation of several of the points is planned for early attention if cir- 

 cumstances permit, and it is hoped that other investigators will carry out similar 

 researches so that definite solutions may be reached. 

 (687) b2 



