OF THE NATIVE DOMESTIC WATER-RECEPTACLES AT LAGOS, &C. 135 



Cypris (2 species). 



Species of this genus occurred in an average of To per cent, of the total 

 receptacles. These Ostracocls have been found in Europe to harbour Tcenia, 

 Trematode larvte and Acantlwcephalus, and therefore deserve further attention. 



Daphnia sp. 



Specimens of this genus were found in only 2 out of 1,0-13 receptacles examined. 



Atthegella africana, Brady. 



This species was present in large numbers but only in one receptacle examined. 

 It was originally found by me in the Gold Coast. 



Summary. 



1. The examination of the contents of the domestic water-receptacles was 

 found to be a practical and accurate method of studying the mosquito fauna of a 

 township. 



2. During the investigation the following points were found to be of 

 importance : — 



a. The Division and District of the township ; for in Lagos conditions differ 

 in diiFerent Divisions. 



/3. The variety of water-receptacles (deep or shallow) ; for some larvaj 

 prefer barrels to pots, and vice versa. 



J. The nationality of the householder. The food of the different nationalities 

 differs, and water-vessels usually contain particles of food upon which 

 larvas may be observed to feed. 



S. The extent of the distribution (Coast line and Inland). The water on 

 the Coast line is mostly brackish, that of the interior is usually almost 

 free from chlorides. 



3. A seasonal variation in numbers was shown to occur, but the causes were 

 obscure. 



4. Sensitiveness to change of environment was found to exist in some cases, 

 and in one was supposed to depend upon the amount of chlorides. 



5. Two active natural enemies of mosquito larvas were found to exist. 



6. It was found that bothlarvre and pupae were killed by raising the temperature 

 of the water above 45° C. 



7. Stef/omi/ia fasciaUi was found to be the commonest mosquito and very widely 

 distributed. 



20419 Di? 



