MALARIA-CARRYING SPECIES OF ANOPHELES 439 



of mosquitoes, and in many respects are less specialized than 

 other members of the family. The different species of the 

 genus vary a great deal as regards choice of breeding places, 

 habits arid appearance, so that it is necessary in any malarial 

 district to determine, if possible, which species are malaria 

 carriers, how they may be identified, where they breed, and what 

 their habits are. The majority of the species have mottled or 

 spotted wings, and the arrangement of the markings is a good 

 means of identification (Fig. 198). 



The following comparative table (Fig. 199) shows in a graphic 

 way how Anopheles may ordinarily be distinguished from other 

 common mosquitoes, such as Culex, Aedes, etc., in their different 

 stages. 



Malaria-Carrying Species. Over a hundred species of Anoph- 

 eles have been described and they occur all over the temperate 

 and tropical parts of the world. Although not more than about 

 half of these species have been proved to be able to harbor ma- 

 larial parasites and nurse them to the weaning point, the num- 

 ber of incriminated species is constantly growing, and it is the 

 safest plan to look upon any Anopheles as a potential malaria 

 carrier until proved otherwise. The fact that a given species 

 of Anopheles may transmit one type of malaria but not another 

 complicates the task of determining the role of a species, and has 

 caused discrepancies in the results of workers. A. quadri- 

 maculatus (Fig. 200) in North America, for instance, may carry 

 tertian and quartan malaria, but not the more deadly aestivo- 

 autumnal type. A. crucians, on the other hand, carries sestivo- 

 autumnal malaria but only rarely carries tertian malaria. The 

 third common North American species, A. punctipennis, has 

 recently been proved to be able to nurse and transmit tertian 

 and quartan malaria, but not nearly so readily as does A. qua- 

 drimaculatus. The situation among these American species 

 fairly illustrates what is found elsewhere considerable differ- 

 ences among the species of Anopheles as regards their ability to 

 nurse the several types of malaria and the readiness with which 

 they may do so. In most countries, though there may be several 

 species which transmit malaria, there is usually one species which 

 is especially responsible for the disease. In North America it is 

 A. quadrimaculatus and in the southern states A. crucians and 

 quadrimaculatus ; in tropical parts of America, A. albimanus and 



