122 



in water. The larvae (Fig. 137) and pupae of mosquitoes 

 breathe by means of air- tubes, and ii is necessary for them 

 to come to the surface in order thai these tubes may come 

 into contact with the air above. In the illustration the 



Fig". 137. Larva of mosquito. 

 {From U. S. Dept. Agric.) 



breathing organ is shown as a projection at right angles to 

 the main axis of the body. 



Control. In order to get rid of mosquitoes, all stag- 

 nant water should be done away with as far as possible. 

 All old tins, bottles, etc., should be removed ; pools should be 

 filled in or drained. Water tanks should be screened in such 

 a way as to prevent the entrance of the adult mosquitoes for 

 the purpose of egg-laying. Many plants are able 

 to hold water in sufficient quantity for the breeding 

 of mosquitoes, and these should be destroyed. Ponds and 

 streams which cannot be done away with should be stocked 

 with millions (Girardinus poeciloides, De Filippi) or other 

 small fish, (Fig. 138) and these will also be found efficient 





wJJ*^ 



mm 



SfVVOCvS*; 



Fig - . 138. Millions. 

 Enlarged. {Imperial Dept. Agric.) 



in the case of garden tubs, fountains, etc., where ornamental 

 plants are grown, as well as in cisterns and tanks which 

 cannot be screened. Kerosene, sprayed 011 the surface of 

 any water in which mosquitoes are breeding, is a very 

 efficient means of destroying them. When the mosquito 

 larvae or pupae rise to the surface to breathe, the kerosene 



