NOTES ON THE BIONOMICS OF GLOSSINA MORSITANS. 



125 



Further evidence in support of the theory hes in the fact that fly was actually 

 found more readily, though not at all abundantly, in the green grass areas away 

 from the vlei, where such game as occurred was grazing, than at the vlei itself. The 

 general prevalence of shade apparently rendered this possible under the prevailing 

 conditions, although this is not usually the case at this time of year. A few fly were 

 even met w^ith in the gusu itself, which was unattractive to the majority of game, 

 but only three w^ere seen in a w^alk of several hours. 



The obvious question is whether the fly had decreased from failure of the birth 

 rate to equal or exceed the death rate, or from the majority having migrated. There 

 was certainly no corresponding increase of fly within a radius of seven or eight miles 

 of the vlei, as the country within this radius was thoroughly explored at the time. 

 Nor had they shifted to the nearest known dry season haunt, which is Matjagenya on 

 the Gadzi Kiver, some seven miles away. There is no evidence of the appearance 

 of fly at any point in this region outside the hmits of the known area, and if the fly 

 had migrated en masse in this direction it must have been noticed, as the country 

 is inhabited. As a matter of fact the natives questioned stated that they knew of 

 no fly outside the previously marked Hmit in this locahty. It would appear, there- 

 fore that if the fly had migrated it must have moved back into the infested country 



