species of Anopheles 53 



The above eleven species of anophelines have been 

 collected in the Canal Zone during the past eight 

 years. They are not taken nor do they exist in their 

 breeding places in anything like equal numbers. 

 For example: Only one specimen of A . gorgasi has been 

 found. Of the eleven species, the commonest ones 

 are A. albimanus, A. pseudopunctipennis, and A. 

 malefactor, but this again must be qualified by stat- 

 ing that the predominance of a species varies from 

 season to season and from place to place. In certain 

 villages, upon going through the barracks only A. 

 albimanus will be found, while in other villages from 

 five to ten per cent, of the mosquitoes will be A. 

 pseudopunctipennis, and at Ancon during October, 

 1908, twenty-seven per cent, were A. malefactor and 

 seventy-two per cent. A . albimanus. A . tarsimaculata 

 appears to be distributed solely near the Atlantic. 

 Mr. A. Busck, of the Bureau of Entomology, United 

 States Department of Agriculture, who collected and 

 made observations on Zone mosquitoes during 1907, 

 gave it as his opinion that A . pseudopunctipennis was 

 the commonest anopheline during the period of his 

 stay. 



The necessities of the Canal operations in excavat- 

 ing and filling change the topography of districts and 

 localities so as sometimes to convert salt marshes into 

 fresh-water ponds, or to make tracts of land contain- 

 ing few anophelines into a vast swamp in which they 

 luxuriate. On the other hand, swamps and breeding 

 places may be drained or filled in the work of excava- 

 tion. These factors, among others, influence the num- 

 ber and variety of species in a locality. 



The commoner anophelines of the Canal Zone may 

 be divided into three groups: 



