RESULTS OBTAINED FROM A MONTHLY EXAMINATION OF 
THE NATIVE DOMESTIC WATER-RECEPTACLES AT LAGOS, 
SOUTHERN NIGERIA, IN 1910-1911. 
By Dr. W. M. GraunaM, 
Director of the Medical Research Institute, Lagos. 
Last year an attempt was made to collect the mosquito larve breeding in the 
vicinity of the Institute at Yaba, near Lagos, and to identify them with their 
imagines. This year it was decided to conduct a similar investigation in the 
township of Lagos itself. My attention had been directed to the importance of 
the subject by the occurrence of an outbreak of Yellow Fever in Sierra Leone and 
the Gold Coast ; and further, I had been requested to suggest a set of instruc- 
tions such as would enable the native Sanitary Inspectors in Lagos to identify 
the larva of Stegomyia fasciata. 
Inherent difficulties rendered it impracticable to draw up any instructions 
which would enable the native Inspectors to make correct identifications, and 
the matter seemed of sufficient importance to warrant 2 complete investigation of 
the domestic mosquito fauna of the Lagos township. 
The investigation was conducted in the following manner. I arranged with 
the Sanitary Department to have the native Sanitary Inspectors instructed to 
empty the contents of each water-receptacle in native yards, found to contain 
mosquito larve, into suitable bottles, which, when labelled with the letters of the 
Sanitary Division and District and the date of collection, were to be forwarded 
daily to the Laboratory. 
On arrival there, the contents of each bottle were transferred to a shallow white 
tray, and examined with a hand-lens, and the various species isolated for more 
detailed examination, or for breeding experiments. As the relative importance 
of separate facts is usually obscure at the beginning of such an investigation, I 
determined to identify and tabulate as completely as possible all living creatures 
found, 
The investigation was begun in August, 1910, by the examination of the 
contents of 364 water-receptacles from native yards in the four Sanitary Divisions 
of the township. I further asked to be supplied monthly with the contents of at 
least 100 water-receptacles from these 4 divisions. The collection of these samples 
was efficiently carried out, except during the months of November and December, 
when the contents of only 43 and 61 receptacles respectively were received at the 
Institute. 
In practice, this method of ascertaining the mosquito fauna of a native town 
has proved relatively easy of execution ; the results have proved more accurate 
and complete than those obtainable by other methods ; and any seasonal variation 
in numbers or distribution can be very readily observed. The catching of 
mosquitos in native yards and houses is difficult, and offers none of the 
advantages gained by dealing with the larve, and even approximate finality is 
