110 WILLIAM F. FISKE — THE BIONOMICS OF GLOSSINA ; 



long been something of a mystery associated with the local distribution of 

 Glossina — not only of G. palpalis, but of other species. Frequent comment has 

 been made of the absence of fly from localities which seemed in every way as 

 suitable for it as others in which it was common. If it is shown that the fly may 

 actually be present permanently and abundantly in localities which are actually 

 unfavourable to its increase, then a new basis for comparison is at once necessary. 



It may very easily be that some localities now fly-free are actually more 

 favourable than other localities now infested ; that they owe immunity to nothing 

 more or less than distance from any such particularly favourable localities as the 

 immediate environs of the Victoria Nyanza seem to furnish in numbers. It is 

 significant that the only feasible method for reducing the numbers of G. palpalis 

 yet suggested is based on what is, in effect, a minor detail in the habits of the 

 adult, i.e., its aversion to localities devoid of shrubby undergrowth. This has 

 nothing directly to do with its breeding habits, its natural enemies, or any other 

 of its very many bionomic characteristics. It appears probable when the 

 favourable breeding grounds are differentiated from, and then compared with, 

 the unfavourable, that constant differences will be noted of as much importance, 

 economically, as the one point of difference between localities frequented and 

 unfrequented by adult flies. 



That which has been written concerns G. palpalis and more particularly the 

 East African race of this species. To what extent it might apply to other 

 species or races, as for example to G. morsitans, is wholly problematical. An 

 attempt has been made to review what is known of the bionomics of G. morsitans 

 and to compare its bionomic history item by item with that of G. palpalis, 

 known or assumed. There are some marked differences, but there are more 

 points of resemblace than points of difference, so far as what is actually known 

 of both species makes direct comparison possible, and it would seem fairly safe 

 to presume that more points of resemblance than of difference will be found as 

 additions are made to our present knowledge. 



Such an assumption is upheld by the circumstance that there is a similar local 

 disparity in the sexes (real or apparent) awaiting explanation ; a similar absence 

 of pathogenic parasites, so far as records go ; and a similar unexplained absence 

 of fly from localities which appear favourable to its existence. The chances 

 would thus appear better than even, that any explanation of these phenomena in 

 the case of G. palpalis will similarly apply in the case of G. morsitans. 



Summary and Conclusions. 



These are presented more as a target for criticism than in the expectation that 

 they will be accepted as a correct exposition of Glossina bionomics. 



(1) In East Africa G. palpalis finds the most favourable conditions for rapid 

 increase in such localities as are represented by certain islands in the Victoria 

 Nyanza and certain spots along the uninhabited lake shore. Here it increases 

 rapidly from generation to generation. 



(2) Inferentially, birds or the large reptiles, and not mammals, furnish the 

 most favourable food. It is^suggested that the results of laboratory experiments 

 to determine the effect of a diet of reptilian blood do not apply literally to the 

 conditions in the open. 



