MOSQUITOES AND MALARIA 217 



human body, undergoing a different history, however. In 

 the mosquito they pass through a new series of changes 

 (Fig. 69, 8-15), finally lodging in the glands around the 

 mouth (salivary glands). If this mosquito with its sali- 

 vary glands thus loaded with these little parasites chances 

 to bite another individual, thrusting its proboscis in 

 through the skin, these parasites will pretty surely be 

 forced into the body of that individual. When the mos- 

 quito flies away it will leave the blood of the one bitten 

 inoculated with the parasites. They are now in a loca- 

 tion adapted to their life and they begin to develop. In 

 a few days they are abundant enough to produce a poi- 

 sonous effect upon their victim and he develops an attack 

 of malaria. Thus this particular disease is transmitted 

 from person to person by means of mosquitoes, and at the 

 present time it seems as if most, and perhaps all, of the 

 cases of malaria start originally from mosquito bites. 

 Malaria is most prevalent at the seasons of the year when 

 mosquitoes are abundant ; it is most abundant in parts 

 of the world where mosquitoes are most common ; and 

 it is most likely to be caught at night, the time when 

 mosquitoes are the liveliest. 



It should be noted, however, that not all kinds of mos- 

 quitoes are capable of carrying this malarial parasite. 

 Fortunately the most common mosquito is quite free 

 from them and is, therefore,* not a source of danger. Only 

 one group of mosquitoes is associated with this trouble. 

 Fig. 70, b, shows the common form of this species, and 

 also the ordinary, harmless mosquito, a. The differences 

 between them are shown in the figures. The most easily 

 distinguished differences are the five delicate hairlike 



