112 MEKBblTil SANDERSON— BLOOD-SUCKING FLIES, &C. 



it occurs in large numbers and enters a tent or house freely. The bites are 

 painful, but rare, owing to the noisy habits of the insect. Can be felt to settle 

 and frequently walks about before biting, especially on clothes. 



Tabanus africanus, Gray. 



Found in thick bush or in " Matete " reeds on the Lake-shore or along rivers, 

 never occurring in large numbers. It bites quickly when it settles, but flies 

 about in a characteristic fashion before settling, i.e., it flies past one very quickly 

 — never round one. Difficult to catch. 



Tabanus biguttatus, Wied. 



Found always near running water, only during heat of the day. Rests on 

 trunks of large trees. Bite severe and causes bleeding. 



Glossina morsitans, Westw. 



There has been a very striking diminution in the number of this species since 

 the onset of the rains. Places where the fly caused great annoyance at the end 

 of November (and during the dry season) are now, to a casual observer, free 

 from it, and only a few specimens can be found after carefid search. This fly is 

 now found in greatest numbers in association with large trees — that is to say, in 

 bush which has never been cultivated — preferably in conjunction with a sandy 

 soil. In such localities the fly is found in as great numbers as formerly, and they 

 bite as freely. 



G. morsitans has been observed to settle, during the hours from 12 to 3, on the 

 sand of small streams preferably where it is dry, but they have also been seen on 

 wet sand, though not for any length of time. I have never seen them go near 

 actual water. 



I have not noticed any disinclination to bite when their victim is stationary, 

 as noted by some. Though they do accompany one when walking or cycling, 

 they seem to me to bite more when one is standing or sitting still. This is based 

 on six months' observation, living in the fly-belt. 



There are two localities (connected by a narrow belt) where the fly is thickest 

 in this neighbourhood, and there is a striking coincidence between this distribu- 

 tion and the occurrence of cases of human trypanosomiasis ; of a total of 14 cases, 

 only one cannot definitely be traced to have been infected in this locality. 



As regards the spread of the fly, I can say nothing from personal experience. 

 I have very definite statements from a resident of 17 years standing that the fly 

 has extended from a small area near Eifu to the present wide-spread area, during 

 8-12 years. His estate was then free from fly, but is now infested with it. 

 Similar statements are made by various members of the Dutch Mission. The 

 occurrence of game certainly coincides with the limitation of the " fly-belt," but 

 so also does " cover," i.e., bush. Both fly and game shun the denuded slopes of 

 the higher foot-hills. 



February, 1911. 



