XVIII] PROPHYLAXIS 319 



enemies and diseases, would be of immense value, and yet up 

 to the present comparatively little work has been done on this 

 subject. 



Bagshawe advises the use of the following measures against 

 the fly : 



(a) The clearing of fly-infested scrub. 



(b) The filling up or draining of pools when it is practicable. 



(c) The cultivation of plants noxious to the fly. 



(d) The destruction of animals on which the fly feeds. 



(e) The encouragement or introduction of animals or 



plants (Fungi) which attack the fly in its adult or 



pupal stages. 

 (/) The collection or destruction of pupae or of the flies 



themselves. 



The clearing of fly-infested scrub has been found to be of 

 great value in Uganda, but it is rather difficult of application 

 over wide areas. As the natural range of palpalis does not 

 exceed 30 yards from the water, a clearance of this strip 

 will cause the disappearance of the fly. According to Roubaud, 

 in the Congo it is sufficient merely to thin out the vegetation 

 on each side of the water, but in most localities it is necessary 

 to remove thoroughly all brushwood and scrub which shelter 

 the fly and its pupae. The cleared areas must either be kept 

 free from scrub-vegetation, or some crop planted which will not 

 give the flies any shelter. Citronella is one of the most suitable, 

 as the grass repays cultivation and its smell may be repugnant 

 to the fly. No clearing should be attempted unless it is possible 

 to make it efficient and keep the cleared spaces free from scrub, 

 and before undertaking any such measure the locality should be 

 carefully examined. The flies and pupae may be restricted to 

 certain parts of the shore, in which case it is only necessary to 

 clear these areas. It is advisable to clear the following locali- 

 ties : boat and steamer landing-places on lakes or rivers ; dipping 

 and washing places ; stations on railways that traverse palpalis 

 areas ; ferries and fords ; and the sites of markets or camps. 



The clearing should be performed during the dry season, 

 because the flies are then less numerous. 



In the Senegal, where clearing has been practised on a 



