MOSQUITO WORK IN KHARTOUM, ETC. 21 



depth of from 25 to 30 feet. The Sheiks of the various districts had orders to 

 see that such " trained " water was not disturbed for forty-eight hours, after 

 Avhich time the users were allowed to remove the oil and take the water. This 

 length of time amply sufficed, aU the larvaj and pupa? present being killed as 

 shown by repeated investigations. 



As a matter of fact the real lethal period was probaljly from about four to six 

 hours, or even less, but it was deemed advisable to let the oil remain for a time as it 

 has been shown that although mosquito eggs may be laid on such oiled waters they 

 will not undero;o further development.' It was of coui'se impossible to make cooperation 



^ ^ ■*■ ^ ^ ^ of military 



absolutely certain that these instructions were always faithfully obeyed, but in the and town 

 great majority of cases the people did as they were told, and any that were 

 refractory were at once reported to the S.M.O., Captain Cummins, who straightway 

 informed the Mudir, and the offenders were promptly brought to their senses. 

 Captain Cunm^iins, indeed, rendered great assistance in the work from an 

 administrative standpoint, and was at all times ready to aid and advise. More 

 recently efforts have been directed to the closing of all unused wells, while, 

 wherever possible, covers have been fixed on those in use and jDumps introduced. 

 Special methods were required in special places. In the Palace Gardens pools had to 

 be cleared of reeds and water-weeds, and in some instances were abolished ; 

 Mr. Sillitoe, the head gardener, very kindly assisting the brigade as much as possible. 



Fish taken from the Blue Nile were tried both in wells and pools. In the closing and 



■*■ covering 



former they speedily died, the water being too hard for them, but in pools containing of weiis 

 river water they proved a success, though after causing the larvae to disappear they 

 too often disappeared themselves, owing to the depredations of natives or aquatic 

 birds. AVhei'ever possible zeers (native water filters) were inspected, and a notice 

 both in English and Arabic was posted in the Sudan Gazette, the official 

 government organ, drawing attention to the role of these earthenware jars as 

 breeding places, and emphasizing the importance of ha^'ing them emptied and 

 cleaned at least twice in the week. iVt an early period the steamers were found to 

 be largely infected, especially Avith the larva^ of Stegoniyia fasciafa, and to a less 

 extent by those of Culex fatigans. Anophelines, either as lai-vse or imagines, have 

 never been met with ; but up-coimtiy, as mil be noted later, the adults are 

 frequently to be seen on board, and may remain as passengers for a considerable 

 period. At first it was decided to use lime for the steamer bilges, but this w\as said, Treatment of 



_ . Steamers 



eiToneously I believe, to act upon iron and to be unsuitable. Consequently crude 

 petroleum was recommended, though not so good nor so easily applied. Along 

 with this the periodical emptying of the bilge and fmnigatiou with the sulphm* 

 squibs described by Colonel Giles - were ad\dsed, the latter to get rid of the adult 

 insects. Unfortunately in the case of the steamers familiarity had evidently bred 

 contempt, for, at first, despite the co-operation of the Director of the Steamei-s and 

 Boats Department, little energy was displayed by the engineers in charge, 

 and the preventive measures were largely ignored, and in some instances even 



> St. George Gray. Jimrnal of Tropical Medicine, 15/10/03 = Giles. " Handbook of Gnats or Mosquitoes " 



