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MOSQUITO LARY^ AND THEIR NATURAL ENEMIES. 



In his Annual Report for one of the districts of the island of Saint Lucia, 

 West Indies, Dr. Lucius Nicholls enters somewhat fully into the above 

 subject. He points out that " it is useless to urge Governments with 

 limited funds to undertake enormous drainage schemes, or to obtain costly 

 apparatus to fill up marshes that are below river or sea level ; other and 

 far less costly methods must be found." While it is admitted that for the 

 wholesale extermination of mosquitos in the vicinity of towns of some size, 

 drainage is doubtless the most suitable and effective method, yet it is urged 

 that in the case of villages and sparsely populated agricultural areas a great 

 deal might be done in the same direction by breeding and distributing the 

 more important natural enemies of the larvae of the ANOPHELiNiE. 



Dr. Nicholls' observations have so far been principally restricted to the 

 two species of Anophelines which occur in his district, namely, Cellia 

 argijrotarsis and C. albipes ; and, as he is careful to point out, his deductions 

 may not apply to other Anophelines, even of the same genus, in other parts 

 of the world. Yet even so, his notes may be of value as indicating the kind 

 of observations and experiments which are likely to be of practical utility, 

 and it may be well therefore to quote them at some length. 



" The following definite statements can be made from notes taken in an 

 extended search for the larvae of these mosquitos [the two species of Cellia 

 mentioned above] : — 



(1.) That their breeding places contain surface food, suspended by grasses 



and other plants growing in the water, or lowly organised plant life 



such as algse growing on the surface, or floating and decomposing 



rubbish. 

 (2.) That in more than ninety-five per cent, of cases their breeding ground 



is non-permanent. That the pools tend to last during, and for a short 



time after, the rains, and they are usually shallow. 

 (3.) They are rarely or never pools in an open piece of land unprotected 



by rocks, bush, or other vegetation, and that tend to be continually 



wind-swept. 

 (4.) They are never pools in which canes or tall reeds and bamboos grow, 



which exclude the light. 

 (5.) The larvae are not found in pools which possess a continuous current 



of water, or if they occur in connection with these pools it is in 



those parts that are protected by vegetation from the current. 

 (6.) The Anophelin.e larvae are not found in close association with their 



natural enemies, nor in any situation that is easily reached by them. 



