5(5 PLAN OP CAMPAIGN AGAINST THE MOSQUITO 



these mosquitos, they argued, should also have been 

 destroyed. 



The explanation is very simple : tlie breeding places 

 of Culex, Stegomyia, and " Anoplieles " are usually 

 quite different. Just as amongst the higher animals 

 some dwell in ca\'es, others burrow in the earth, and 

 others again live in tlie forest, so with the different 

 species of mosquitos, tlie Culex prefers dirty gutters 

 and drains, tlie Stegomyia wooden barrels and small 

 receptacles of all kinds, the Anophelines pools, the 

 margins of marshes, lakes, rivers, ponds, and small 

 receptacles coated with a lining of humus. Fish will 

 not be found in the dirty gutters or in drains, nor 

 yet in the water-barrels and small receptacles. So 

 Culex and Stegomyia under these circumstances are 

 not molested, but the larvae of the Anophelines are 

 exposed to the fish. That this is the explanation 

 I had a further proof in Barbados ; I found that 

 amongst the natives there was a very common practice 

 of keeping one or two small gold fish in the drinking- 

 water barrel. Now, wherever I found this to be the 

 case I never found the Stegomyia larva? present ; 

 where these fish were absent the larva? Avere invariably 

 present. A\'^hen I asked the native residents why they 

 kept fish in their drinking-water barrels, they always 

 replied that they liad been taught to do so by either 

 their parents or grandparents, and for this reason : if 

 a maliciously inclined neighbour poisoned the water, 

 the gold fish would die, turn up and float on the 

 surface, and they could see at once that the water 

 was poisoned ; then they would pour out the contents 



