100 



Insects and Disease 



they are not of sufficient importance to have any 

 appreciable effect on the number of mosquitoes in 

 a badly infested region. 



ENEMIES OF THE LARV7E AND PUP^ 



The larvae and pupae on the other hand have 

 many important enemies. Indeed under favorable 

 conditions these may keep small ponds or lakes 

 quite free from the pests. The predaceous aquatic 

 larvae of many insects feed freely on wrigglers. 

 The larvae of the diving beetles which are known 

 as water-tigers are particularly ferocious and will 

 soon destroy all the wrigglers in ponds where they 

 are present (Fig. 92). Dragon-fly larvae also feed 

 freely on mosquito larvae. Whirligig beetles are 

 said to be particularly destructive to Anopheles 

 larvae and many other insects such as water- 

 boatmen, back-swimmers, etc., feed on the larvae 

 of various species. A few of these introduced into 

 a breeding-jar with Anopheles larvae will soon de- 

 stroy all of them, even the very young bugs attack- 

 ing larvae much larger than themselves. 



It is interesting to note that the larvae of some 

 mosquitoes are themselves predaceous and feed 

 freely on the other wrigglers that may chance to be 

 in the same locality. 



Various species of fish are, however, the most im- 



