72 TROPICAL MEDICINE AND HYGIENE 



in favour of such a view, and it is exceptional for protozoa 

 to be equally capable of similar development in widely 

 separated groups of arthropoda. 



The success of prophylactic measures used on the 

 hypothesis that certain mosquitoes are the carriers of 

 malaria shows that this at any rate is the important 

 method of the propagation of malaria. If, when the 

 possibility of this method of conveyance is removed, 

 malaria still continued to exist in any place, special 

 inquiry would be required, but no such instances are 

 known at present. For prophylactic work, therefore, 

 the known method in which the disease is carried is the 

 only one now to be considered. 



Some knowledge of insects in general, and of mosquitoes 

 in particular, is essential to advise as to economic prophy- 

 lactic measures, and an outline of the classification of 

 insects, and the principles on which the mosquitoes are 

 classified, is given in a separate chapter as an appendix. 



All known carriers of malaria belong to the division 

 of the mosquitoes known as Anopheliiicc. The different 

 species of anophelines do not serve equally well as carriers 

 of malaria. Some species are readily infected, others only 

 with difficulty, and some not at all. The dangerous species 

 are those which are both numerous and readily convey 

 the disease. 



For economic and efficient prophylaxis a knowledge 

 of the habits of each species is required, and it is found 

 that the different species vary greatly in their habits, life- 

 history, and breeding-places. 



In any place or country the species of anophelines 

 must be determined ; those that are good carriers of 

 malaria must be found out experimentally, and the 

 breeding-places and habits of these must be studied in 

 great detail. 



The anophelines, which include all the known carriers 

 of human malaria, are easily distinguished from other 

 mosquitoes, which have a straight, penetrating proboscis. 



(i) The palps in both male and female are practically 



