438 



MOSQUITOES 



Mosquitoes and Malaria 



As was shown in Chap. IX, malaria is one of the most important 

 and one of the most deadly of human diseases. This being true, 

 the mosquitoes, which arc the sole means of . transmitting the 

 disease, must be looked upon as among the most important and 

 most deadly enemies of the human race. The role of mosquitoes 

 in causing disease, especially malaria, has been suspected by 

 various peoples as far back as any records go. The steps which 

 led to the yroof of the relation of mosquitoes to malaria are briefly 

 outhned on pp. 148-149. 



Fortunately not all mosquitoes are malaria carriers; in fact, 



only one genus, Anopheles, com- 

 prising a number of more or less 

 well-defined subgenera which have 

 been considered genera by some 

 workers, is known to be able to 

 transmit the human malarial dis- 

 eases, and not even all of the 

 species of this genus are incrimi- 

 nated. As will be seen below, 

 some species of Anopheles are able 

 to transmit one type of malaria, 

 but not another. A species of 

 Culex has l^eeii shown to be instru- 

 mental in transmitting a disease 

 of birds which is allied to malaria. 

 The role of the mosquito in the 



Fig. 198. Wings of American 

 Anopheles; A, A. crucians; B, A. quad- 

 rimaculalus; C, A. punctipennis; D, 



A.rdfnmanns. Drawn to scale. (After spread of malaria and the develop- 



Howard, Dyar and Knab.) '■ _ _ ' 



ment of the parasites in the mos- 

 quito's body have been discussed in Chap. IX, pp. 154-156. Suffice 

 it to repeat here that the sexual phase of the life history of all 

 malaria parasites occurs in the iligcstive tract of mosquitoes, after 

 which a rapid multiplication of the germs takes place, resulting 

 ultimately in the collection of large numbers of the parasites in 

 the salivary glands of the insect, whence they are poured into the 

 capillaries in the skin of the subsequent victims of the mosquito. 

 Identification of Anopheles. — The Anopheles mosquitoes, 

 fortunately, are fairly easy to identify in all stages of their de- 

 velopment except as pupa;. Th( y represent a primitive group 



