30 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
Sample of Water 
Chlorine per 100,000 parts 
Chlorine expressed as per- 
centage of NaCl 
I. 
Public well, New Town, no mosquitoes 
present in water 
I 6 I ■ 2 
•26c 
J 
2. 
Public well, Lancaster Street, water rather 
foul, Anopheles larvae present in numbers 
1 148-0 
1-89 
3- 
Public well in Clifton Road, behind Hospital, 
no larvae present 
186-0 
0"3 
4- 
Water (tidal) found in drain near sluice gate, 
Blucher Street, A. costalis and large quan- 
tities of C. halasstos present 
1038-5 
I-7I 
5- 
Small well in private garden, Culex present, 
few onl)'... 
27-9 
0-04 
6. 
Small well in native compound, Victoria 
Street, Culex larvae present 
1 145-0 
i-88 
Mosouitoes Present in the Gambia 
The commonest mosquitoes met with in Bathurst were Stegomyia fasciata and 
A. costalis. After these may be mentioned Culex fatigans, Culex duttoni, Culex halassios ; 
the latter, a new species, was especially frequent in December and January, and bred 
in the tidal pools of water as described above. While in Bathurst I never saw 
specimens of A. funestus. Out of a series of Anopheles which had been bred, or 
captured in various parts of the town, Mr. Theobald has failed to detect one ; on the 
other hand, at Baia and McCarthy Island, in the Hinterland, I did not obtain a single 
A. costalis ; here all the Anopheles caught were the small A. funestus and its varieties. 
At Baia, out of two hundred mosquitoes brought to me by natives, all were A. funestus 
except one ; these mosquitoes could be caught at any time of the day in the native 
huts, they were found resting on the wall, some had evidently fed not many hours 
previously; the ovaries were in all stages of development. At McCarthy Island 
I found, at i p.m., a great many A. funestus on the walls of a room in Government 
House in which a European slept. No other kind of mosquito was present. At 
Baia and McCarthy Island, in December, when everything is dried up, the river and 
a few marshes were the only available breeding-places. At Baia the river was three 
miles away from the town, and the only marsh near was two miles away. The 
only breeding-place in the native town was an old disused well, which was found to 
be thirty-four feet deep ; at this depth only Culex larvae were found in the water. 
At McCarthy Island I never found mosquito larvae in the river, but in a swamp halt- 
a-mile away from the town they occurred in great numbers. At the Cape, where a 
similar marsh to the one on McCarthy Island occurred, A. funestus was the chief 
mosquito found in the native town ; but here A. costalis was also present in 
