﻿PLACES OF ANOPHELES IN SAINT LUCIA, BRITISH WEST INDIES. 265 



Probably there are numerous factors which apply to all countries and to all 

 species of Anophelines ; but on the other hand, many important points may be 

 found to be modified in different localities and for different species. 



The necessity for carrying out examinations throughout the year has here been 

 amply indicated. For instance, there are many places in this island which are 

 the real sources of the malaria in the neighbourhood, but unless they are visited 

 after continuous rains have water-logged them, their true importance cannot be 

 appreciated. 



The majority of visits would be fruitful in showing larvae to be present in 

 certain overgrown streams, gutters or pools, and money might be spent in 

 " canalising " or filling up these with little or no reduction of the malaria, as the 

 occurrence of the disease actually depends upon myriads of mosquitos being 

 occasionally bred out on water-logged and protected marsh-land ; and this fact 

 might only come to light after repeated visits. All places which breed 

 Anophelines should receive attention, but this should be directed according to 

 the relative importance of the breeding-grounds. 



The following are instances of what may occur from the lack of adequate 

 investigation. 



In one case it was intended to employ a large amount of kerosine oil on lagoons 

 in malarial neighbourhoods. These lagoons, however, never breed mosquitos and 

 are teeming with fish, whereas in the surrounding swampy pastures, which it is 

 impossible to oil, larvae are numerous ; though they are slightly kept in check by 

 the fish which are carried from the lagoons after heavy rains. The result of 

 oiling might have been disastrous, if it had killed out the fish and other natural 

 enemies ; in any case it could have been of no value. Kerosine oil is un- 

 doubtedly of great value for tanks and butts, but as an Anopheline larvicide, its 

 use should be considerably restricted, as much damage may be done. In this 

 island there are few, if any, situations where its use could be advised. 



In the second case a road-side gutter was found to contain larvae at certain 

 times, but as there was a small stream continually passing through it and it was 

 on a hill-side, the larvae were frequently washed away, and could never develope 

 if the gutters were kept clean. The gutter was filled up and the stream was 

 carried away by culverts, with the unfortunate result that the water was directed 

 to a piece of land which became water-logged, and thus one breeding place was 

 merely replaced by another of a worse type. 



