ANIMALS AS DISEASE CARRIERS 399 



the water is covered with oil, the larvae are unable 

 to breathe through this tube and so they die. When 

 the larvae change to the pupa stage they still remain 

 under the surface of the water, breathing through 

 a tube, but they do not eat. In the pupa stage, wings 

 and legs and other necessary organs for the activi- 

 ties which they perform during the adult period are de- 

 veloped. The adult mosquito flies about and lives as a 

 parasite upon other living animals by forcing its proboscis 

 into the skin of the animal and extracting blood. This 



MOSQUITOES IN RESTING POSITION 



On the left the malarial mosquito (Anopheles); on the right the harmless 

 mosquito (Culex) (From Howard's Mosquitoes). 



habit of obtaining food makes it possible for the mosquito 

 to carry a disease from one person to another. If the 

 A nopheles mosquito secures a meal of blood from a person 

 who has malaria fever, it will take some of the germs into 

 its body; these will pass into the stomach, thence into 

 the blood of the mosquito, and into its salivary glands, 

 and then when it bites or secures a meal from a person 

 who does not have malaria fever, some of these germs are 

 forced out from its salivary glands, thus conveying the 

 germs to a healthy person, who then becomes a subject of 

 the disease. The mosquito known as the Culex does not 

 carry any disease. The Culex lays its eggs in rafts, usually 



