90 INSECTS AND MAN 



and Culex quinquefasciatus. Stegomyia is exceedingly 

 domestic in habit, and is never found, except by accident, 

 away from man's dwellings. Anopheles albimanus is the 

 most abundant of the Isthmian species of Anopheles, and 

 it shows greater persistence in biting man and entering 

 his houses than any other species. Needless to say it is a 

 vector of malaria ; in fact, it has been shown that a greater 

 percentage of the females of this species become infective, 

 and capable of transmitting the malaria blood parasite, 

 than do those of any other species. Another mosquito of 

 similar habit is Anopheles tarsimaculata, and it, also, is a 

 transmitter of malaria. Anopheles pseudopunctipennis is 

 not so common as albimanus and tarsimaculata, nor is it 

 so closely associated with man ; it is, however, a malaria- 

 carrier, though experiments have shown that, under similar 

 conditions, only one individual of this species becomes 

 capable of transmitting malaria, to five of albimanus. 



It will be gathered that considerable effort is required to 

 keep this host of disease-carrying insects under control in 

 the Canal zone. The work is carried out by the Division 

 of Sanitation, by whom a chief sanitary inspector and 

 his assistant, three division inspectors, and twenty-five 

 inspectors are employed and apportioned among seven- 

 teen districts. " Each district inspector is held responsible 

 for the physical condition of his station as it affects the 

 breeding of mosquitoes, and indirectly for the 'malarial 

 rate,' or cases of malaria occurring each week as expressed 

 in terms of percentage of population." A regular pro- 

 gramme of oiling is drawn up by him, and executed by 

 the foreman of oilers; native and American towns are 

 inspected for Stegomyia and Culex breeding places, and 

 most detailed reports are forwarded to headquarters each 

 week. It was not till the Americans began the cutting 

 of the Panama Canal that the work of controlling and 

 eradicating the twin pests of tropical America yellow 

 fever and malaria was taken in hand. At the time of 



