8 



do not breed in all puddles, but only in those which suit 

 them ; and with a very little trouble it is possible to detect 

 at sight the kind of water in which the larvae will be found. 



They are not often found in large bodies of water, such 

 as lakes, where the surface is constantly ruffled by the 

 wind, and where there are many fish to eat them ; nor in 

 large rivers ; nor in rushing torrents ; nor in well-contained 

 ponds ; nor in small but deep pools ; nor indeed do they 

 thrive much in the deeper parts of marshes and mangrove- 

 swamps. Nor, on the other hand, do they care for very 

 small collections of water, such as the temporary puddles 

 which form on the ground during a shower of rain ; because 

 in such puddles the larvae perish almost at once as soon as 

 the water dries up. 



In my experience in India and Africa, Anopheles larvae 

 are found chiefly in small shallow puddles on the ground 

 which are not so large as to contain minnows and water- 

 beetles, nor so small as to dry up too quickly. Such 

 puddles are frequently found in depressions in the ground, 

 in badly made drains and gutters, in places where water 

 constantly oozes from the soil during the rains, or where 

 the drainage is checked by out-cropping rock or by em- 

 bankments and walls, or where water constantly escapes 

 from pumps, stables, bathrooms, and irrigation channels. 

 Small pools containing green mould or water-weed are 

 much affected by the larvae ; and so are pools contained on 

 the surface of weather-worn rock. But on the other hand, 

 however favourable for the larvae a pool may otherwise be, 

 it becomes quite unsuitable for them if it be at all exposed 

 to scouring during heavy rain ; because, in this case, when- 

 ever a heavy shower falls, the larvae are sure to be swept 

 into rain-torrents and lost. It is indeed for this reason 



