MOSQUITO WORK IN KHARTOUM AND IN THE ANGLO-EGYTTIAN SUDAN GENERALLY 



lias been reduced to lialf-a-pint. Tliis is still much in excess of what is actually required to 

 kill the larvffi. Two ounces have been found to be ample, but the larger quantity is employed 

 because some is wasted owing to splashing, and because it admits of a film being formed 

 which lasts for several days in the case of a well and prevents reinfection. 



Several interesting new facts have come to light. Thus, wells which are constantly in 

 use are very rarely infected by Culices. It is the unused well that is the great nuisance, 

 and very often the unused well is in the unoccupied and locked-up premises, and therefore 



difficult of access. 

 Sometimes a used and 

 unused well have been 

 found alongside each 

 other, the former un- 

 infected, the latter 

 harbouring eggs and 

 larvffi. Sir William 

 Maegregor, till lately 

 Governor of Lagos, 

 wrote me from New- 

 foundland, asking if 

 the depth of the wells 

 some observations on this 



Unused and 

 deep wells 



Fig. 9. — Develoi'Mknt of Mosquitoes. Larv.«, PupvE and Imagines. Both Culex and 

 Anopheline larvae are shown, the former only possessing respirating sj'phon tubes. 



Fig. 10. — Egg-doat of Culex. The straight line indicates 

 the level of the water. 



had any influence on the breeiling operations, as he had made 

 point in the West Coast territories. 



In Khartoum the deepest wells do not exceed 30 feet from ground level to water surface, 

 and C. fat'ujinifi seem to breed indiflerently up to that depth. The wells at Omdurman are 

 much deeper. In one of these, at a depth of 70 feet, the larvaj of both C. faf'njdii.f and 



P. co-italix were found. It was an uncovered 

 well worked by a pump, and it is remarkable 

 that Anophelines were found in it, for there 

 could be but little light ;it that depth, and as 

 stated, P. costaU-s does not favour wells. So far it has not been possible to attack the 

 mosquitoes in Omdurman. The area there is too vast, it is out of the way, few Europeans 

 live in it, and the distance between it and Khartoum is, I think, too great for infections of 

 the latter town from the former to occur with any frequency, save, indeed, when the inevitable 

 steamer serves as an intermediary. Still the task should be undertaken, but it is largely a 

 question of ways and means. Dr. Doty's recent investigations* go to support the view that 

 the mosquito is not much of a voluntary traveller. It is worth noting that the wind very 

 rarely blows from Omdunnan to Khartoum, ij\. from the north-west. The reverse is the 

 ease in the summer, while in the winter north-east or due north winds prevail. 



Considerable improvement has resulted from having as many wells as possible covered 

 over, permanently if a pump is affixed, with a movable wooden cover if the water is drawn 

 by hand. Wooden covers are very liable to warp and split in tliis country, but they can 

 be easily repaired. An attempt was made to procure covers of canvas or sacking fixed to 

 barrel hoops, like those used with success at Bathurst.f In Khartoum they cost too much, 

 chiefly because barrels are rare articles in the Sudan, and special flexible metal had to be 



* Brit. Med. Jour., Vol. II., 1905, p. 971. 

 t Dutton. Report of the Malaria Expoditiou to the Oamljia, 1002, p. .30, 



Considerations 



regarding 



Omdurman 



Covering of 

 wells and the 

 introduction of 

 pumps 



