IX] MOSQUITOES AND MALARIA I4I 



for some reason, A. rossii is not an active transmitter of 

 malaria, if it transmits at all, under natural conditions. 



Another species not suitable as a carrier, and which in this 

 case was refractory even to experimental infection, is the 

 North American species Anopheles punctipennis. In this case 

 A. maculipennis and A. punctipennis were fed together on an 

 infected patient ; the former became infected whilst the latter 

 remained free from infection. 



The development of the three species of malarial parasites 

 does not take place with the same facility in any given species of 

 mosquito. Thus Kinoshita found that in Formosa, Plasmodium 

 falciparum was incapable of development within A. {Myzo- 

 rhynchus) sinensis, whilst this species of mosquito could easily 

 be infected with Plasmodium vivax (seven times out of eleven) 

 and less easily with Plasmodium malaricB (one in seven). In 

 the same region A. {Myzomyia) christophersi almost invariably 

 became infected when fed on a patient containing the gametes 

 of P. falciparum in his blood. 



Other species have also been noted as probably not taking 

 an active part in malaria transmission or to be actually refrac- 

 tory to experimental infection with the malaria parasite. 



But though some species are possibly incapable of acting as 

 hosts, and whilst some are more suitable hosts than others, there 

 is reason to believe that very many of the species are at least 

 potential transmitters. Thus in India, Stephens and Ghristo- 

 phers succeeded in experimentally infecting all but one species 

 out of a considerable variety of Anophelines. Similarly, 

 Darling at Panama has produced infection in many of the 

 Anophelines of that region. 



The most important point in regard to the transmitting 

 power of a species is the extent to which it is found actively 

 concerned in transmission under natural conditions. In this 

 respect there are certain species which must be looked upon as 

 the chief carriers in particular parts of the world. 



In Europe the common carrier is Anopheles maculipennis, 

 but the common species, Anopheles bifurcatus, is also capable 

 of transmitting malaria. A. maculipennis is the common 

 carrier in the Mediterranean islands and is largely concerned 



