Domestic and wild species. 



which carry off the water from the stand-pipes, and in the small 

 stone reservoirs in the gardens. 



These facts point to the necessity of constant and careful 

 search in every collection of water when any efforts at extermination 

 of larvae are attempted, and although we may certainly say that 

 under favourable conditions we are more likely to find " anopheles " 

 larvae in certain collections of water than in others, and that under 

 such conditions the different species will select different kinds of 

 breeding places, no hard-and-fast rule, which might perhaps prevent 

 us from searching a particular place, can be made. 



DOMESTIC AND WILD SPECIES. THE DIFFICULTY OF ESTIMATING THE RELA- 

 TIVE ABUNDANCE OF DIFFERENT SPECIES. 



It is a well recognised fact that some species of " anopheles " 

 are more commonly found near villages and dwellings than others. 

 We may, in fact, divide these insects broadly into two classes : the 

 " domestic " species, which are usually found near human dwellings, 

 and the " wild " species, which are rarely found in houses. Of the 

 first class, A. rossi is a typical example, and of the second A. bar- 

 birostris. Some species would appear, as regards this habit, to 

 occupy a place intermediate between the typically domestic and 

 the typically wild species. A. fuliginosus, for example, may, in 

 certain parts of India, be found in enormous numbers in the sheds 

 and outhouses on the outskirts of a village, while in other parts, 

 though large numbers may be caught in tents pitched at some 

 distance from a village, few or none will be found in the houses of 

 the village itself. 



It is usual to say that the greater the number of " anopheles " 

 there are in a place, the greater will be the prevalence of malaria. 

 This is not by any means borne out by experience. We have 

 already mentioned that some species of " anopheles " are better 

 malaria-carriers than others, and apart altogether from the fact 

 that " anopheles " may be abundant in a place without there being 

 any malaria there at all, it often happens that the species which 

 is present most abundantly is not the one which is carrying malaria 

 at the time. It is, however, a difficult matter to estimate the 

 relative abundance of different species in any place, for some are 

 much more easily seen than others, and the habits which some 



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