﻿PLACES OF ANOPHELES IN SAINT LUCIA, BRITISH WEST INDIES. 263 



(c.) In the examination of numerous crab-holes, which usually teem with 

 Deinocerites cancer, I have but once found an Anopheline larva, a single specimen 

 of A. albimanus. 



(d.) In the centres of lagoons, ponds, and running streams, I have never found 

 them, though searches have been conducted from boats. In this island these 

 situations contain very numerous fish. 



(e,) Pools in barren rocks through which a stream continually but slowly 

 runs. The temperature of these becomes very high as they are exposed to the 

 direct rays of the sun, and there is very little food for larvae. I have never 

 found Anophelines in such places. 



Summary of Breeding Places, 



1. Non-permanent. — These produce more Anophelines than all the other places 

 put together, and in this island, and probably throughout the West Indies, they 

 are the principal cause of malaria. 



2. Altered permanent. — Produce far less Anophelines than the permanent, but 

 are often more apparent, and more easily studied. 



3. Permanent. — More apparent than 1 and 2, but relatively unimportant. 



4. Miscellaneous. — Anophelines do not breed in these situations, though an 

 occasional exception may occur. 



The Effect of Rainfall upon the Numbers of Anophelines. 



It is not so much the amount as the nature of the rainfall that tends to promote 

 the breeding of Anophelines. The amount of rainfall varies greatly in different 

 localities in St. Lucia (Table II); thus in the year 1909, the least rainfall 

 recorded was 61*23 in., and the greatest was 124*14 in. The latter amount fell in 

 the densely clad forest heights, and the former on a small stretch of open country 

 near the sea-shore ; these two points are separated from each other only by about 

 ten miles. The average rainfall from fifteen gauges situated in different parts of 

 the island was for this year 86*6. 



Provided over 60 inches of rain falls, the nature of the locality is of more 

 importance than the yearly amount of rain. Thus two localities having a rainfall 

 of 62*97 and 95*65 inches respectively are notoriously malarious, whereas two 

 other places with 61*23 and 97*01 inches are almost free from malaria. 



Most of the dense forest heights are free from Anophelines, for the continuous 

 rainfall tends incessantly to wash out the hill-side pools ; the temperature also 

 is low, and the giant vegetation screens the pools from sunlight. 



The rainfall for March 1909 (Table III, col. i) is typical for a month in 

 the dry season ; all the the non-permanent pools quickly dry up, and many 

 permanent ones become very low and stagnant. Very few Anopheline larvae 

 can be obtained in months of this kind. 



October 1909, was a typical month of the wet season (Table III, col. ii) ; 

 the rainfall, however, in some parts of the island was too uneven to be very 

 favourable for Anophelines. Thus the period of dry weather recorded in 



