MALARIA EXPEDITION TO THE GAMBIA 
23 
No. Examined 
No. of Wells 
covered 
Presence of 
Anopheles larvae 
Anopheles and Culex 
type of larvae 
Culex type oi 
larvae 
Tub wcl Is • ■ • 
? 1 7 
z 1 / 

I 98 
Stone wells — 
Public 
'4 
I 
1 
Private 
5 5 
1 3 
I 
8 
3 5 
From the above table it will be seen that over ninety per cent, of the small tub 
wells already examined were breeding mosquitoes. With regard to the large private 
wells those in which larvae were found were generally the ones improperly covered. 
In this connexion it is interesting to record the examination of a large stone well in 
the yard at the Police Station, which was extremely well covered in, the only entrance 
as far as one could detect on superficial examination was the small wire gauze lid. 
In the early part of my stay in Bathurst I had not detected any mosquitoes in the 
water, in December this well became foul ; it was emptied and cleaned, but afterwards 
the water was worse than ever, having a very strong smell ; the contamination was 
very probably due to a leaking midden in the neighbourhood. Orders were then 
given that no water was to be taken from the well, and the small lid was locked. 
Before the filling in of this well was accomplished I examined this well and found 
mosquito larvae were present in it, and many young mosquitoes dead on the surface 
of the water. On closer examination of the well I discovered two small holes 
between the stone rim and wooden cover. These two holes were the only means by 
which mosquitoes could gain entrance into the well to lay their eggs, but the young 
mosquitoes apparently had failed to detect these exits and had died in their endeavours 
to get out through the wire gauze of the lid in the cover. It will be seen how 
important it is for wells to have a perfectly fitting cover. The mosquitoes which 
breed in the wells at Bathurst during the latter part of the year are : 
Anopheles costalis (chiefly in the large built wells) 
Culex fatigans 
Stegomyia fasciata 
Culex tigripes 
Culex duttoni 
