XVl] BIONOMICS 281 



In these places there is hght forest with fairly short grass 

 and occasionally open glades, whilst game is abundant, a 

 combination which is ideal for the flies. From these regions 

 they extend into the surrounding country along connecting 

 forest as soon as the conditions become suitable, and this 

 extension may easily be observed. 



Dr Shircore, therefore, advocates the destruction of the 

 primary centres by means of clearing and bush-fires, during 

 the height of the dry season, when there are very few tsetse- 

 flies in the surrounding country. As these primary centres are 

 often of very limited area, the destruction of the fl^^ in these 

 regions is a prophylactic measure that might easily be adopted, 

 instead of the game destruction and wholesale clearance of the 

 country which is being advocated by certain individuals. 



The fly will feed with avidity on almost any large manmial 

 or bird, and does not seem to be dependent on any particular 

 species for its food-supply. In Nigeria, Simpson noticed that 

 these insects seem to have a great predilection for baboons, 

 enormous swarms accompanying the herds of these animals, 

 and in the Bahr el Ghazal, Selous has noticed the same pecu- 

 harity. 



Usually G. morsitans becomes active about sunrise, dis- 

 appears during the hottest hours of the day and recommences 

 to bite when it becomes cooler and also after the sun has set. 

 Other observers, however, state that it is most aggressive 

 during the hottest hours of the day. Occasionally they will 

 feed at night, especially if a bright moon is shining, and some- 

 times even in its absence. As a rule the flies disappear during 

 a shower, but they have been known to bite during heavy rain. 



Like G. paipalis, the present species is especially attracted 

 by moving objects, but quickly leaves them as soon as all 

 motion ceases. Thus Montgomery and Kinghorn note that 

 even in its natural haunts, G. morsitans will quickly retreat 

 from a person coming to a halt, although they may have been 

 pestilent immediately prior to this. 



In addition to being attracted by dark colours, Newstead 

 found that the shades most preferred by this species were 

 khaki and yellowish-green, whilst white was the least attractive 



