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THE DOMESTIC MOSQUITOS OF ACCRA. 



By J. W. Scott Macfie, M.A., D.Sc, and A. Ingram, M.D., CM. 

 {West African Medical Staff). 



(Maps I & II.) 



Samples of water containing mosquito larvae are collected at Accra by the Sanitary 

 Inspectors, and are sent regularly to the Laboratory for identification. The number 

 of samples submitted in this way is never very large, and varies considerably from time 

 to time ; but, recently, a careful examination has been made of all the specimens 

 received during a complete year, and it is proposed to analyse in this paper the materials 

 thus collected. In 1910-1911 Graham* made a similar study of the larvae found in 

 native water-receptacles at Lagos, and it will therefore be interesting to compare our 

 results with those obtained by him. 



Accra, the capital of the Gold Coast Colony, is situated on the coast a few miles 

 west of the meridian of Greenwich and about 330 miles north of the Equator. The 

 town itself is divided into three portions, Accra proper to the west, Christiansborg 

 where the Governor resides to the east, and the official residential area Victoriaborg 

 between these two. The surrounding country is level for some miles, but the actual 

 site of the town slopes slightly upwards as it recedes from the sea. Accra is a very 

 dry and dusty town, almost completely denuded of vegetation. The rainfall is low ; 

 during the twelve months under consideration, December 1914 to November 1915, 

 21*75 inches of rain fell. During the same period the maximum shade temperature 

 averaged 85"39°, the minimum 73*83°, and the relative humidity 72*46°. The physical 

 features and climatic conditions of Accra differ therefore greatly from those of Lagos, 

 a low-lying town surrounded by swamps with an average rainfall of about 70 inches. 



Each of the samples containing mosquito larvae was marked with the number of 

 the house and the division of the town from which it came. For the purposes of 

 sanitary organisation Accra is divided into seventeen areas or blocks, and Christians- 

 borg into seven. The positions of these are shown on the accompanpng outhne 

 map (Map I). Victoriaborg is not divided into blocks, but each house is numbered. 

 Practically, however, Victoriaborg may be disregarded, since with the exceptions of 

 one or two samples all the larvae submitted had been found in the native compounds 

 in Accra and the village of Christiansborg. A few samples were also collected from 

 such situations as the lagoon and the Victoriaborg Reservoir and these are included 

 in Table III, but are excluded from Table I, which summarises the identifications of 

 the purely domestic mosquitos. 



* BuU. Ent. Kes., u, p. 127. 



