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.