120 KUPERT W. JACK. 



better feeding grounds are to be found. Or, finally, do they migrate individually ? 

 In the latter case they might take many directions and a corresponding increase 

 in another part would not be hkely to accompany the decrease in the original 

 centre. Fortunately for the neighbouring settlers, where we have had a clear case 

 of hunger conditions as regards game, in the Hartley district, the diminishing fly 

 became gradually restricted in range as the game decreased, and still adhered to 

 their old haunts, whilst numerous cattle worked with more or less impunity amongst 

 the Shagari mines a few miles away on the one side, and settlement proceeded 

 along the railway hne with rapidly decreasing losses on the other. The destruction 

 of the usual haunts by the felhng of the forest did, however, appear to cause a scat-' 

 tering of the tsetse, which died out, probably in consequence. The fly along the 

 Gorai River, mentioned above, were obviously very hungry at the time of the writer's 

 visit in November 1910 (out of some 82 flies caught actually more were females 

 than males), and from all accounts this is an annual occurrence at this spot ; but 

 although game was more abundant on the Hunyani a few miles away, the flies 

 apparently preferred to endure hunger in this area rather than migrate. They 

 were not, it must be confessed, absolutely starving, as wart-hog and duiker were 

 actually seen in the fly haunts ; but their meals were without doubt sufficiently 

 irregular^to keep the appetite of the majority very keen. Fly, on the other hand, 

 was comparatively scarce on the Hunyani where more game was to be found. 



The writer has, in fact, been able to find no evidence during the past ten years 

 in this territory that the fly has any tendency to migrate, apart from the seasonal 

 scattering during the wet season, as a result of which the pest is much more uni- 

 formly distributed over the infested area than during the dry season. Although 

 new areas have been invaded by its gradual spread, no incursion of fly into locahties 

 other than those immediately adjacent to the former infested areas have occurred. 

 It is readily admitted that an apparent migration might take place in the course 

 of time, the fly increasing in a newly invaded area and decreasing in the old, but this 

 does not imply migration. In any case in Southern Rhodesia the invasion of new 

 areas, in the writer's experience, has not been accompanied by any corresponding 

 reduction elsewhere, nor has reduction in an old area been accompanied by any 

 noticeable increase elsewhere. The fly appears to increase or decrease in any area 

 solely in relation to its abihty to breed successfully. 



On the whole there seems httle reason at present to beheve in any form of 

 migration in respect to Glossina morsitans, other than the seasonal scattering with 

 the advent of the wet season, and forced movements induced by destruction of the 

 forest. In the latter case the fly naturally follows the receding shade. 



The Question of Fly moving about Infested Areas with Game. 



The idea that fly locates game and follows its movements more or less continuously, 

 at least within the limits of infested country, is not absent from the writings of 

 serious investigators. In this connection it is essential to distinguish between 

 following for a limited distance, as is the well-known habit of the males, and possibly 

 of the females to a much less degree, and the alleged habit of the fly attaching 

 itself to the herds and accompanying them in their wanderings day after day. The 

 writer has been able to find no direct evidence adduced in support of this idea, 



