MOSQUITOES AND DISEASE 87 



have never been seen and we can only judge of their nature by 

 comparing the disease they cause with other similar diseases. 



FIG. 53. A, position of malaria mosquito (Anopheles) when at rest. 



B, position of common house mosquito (Culex) when at rest. (After Howard.) 



THE MALARIAL MOSQUITO 



Malarial fever is caused by minute parasitic Protozoa which 

 attack the blood corpuscles causing " chills and fever." This 

 was first demonstrated by a French army surgeon in Algiers 

 in 1880. Three kinds of malaria are recognized : (i) Tertian 



FIG. 54. A, position of larva of malaria mosquito at surface ot water. 



B, position of larva of common house mosquito at surface of water. 



C, raft of eggs of mosquito floating on surface of water. 



D, eggs of house mosquito ; E, eggs of malaria mosquito, f After Howard.) 



