326 



BIOLOGY AND HUM.\X LIFE 



128 



1870 1880 1890 1895 1897 1899 1901 

 1896 1898 1900 



Fig. 155. The reduction of 

 yellow fever in Cuba 



The mortality from this disease 

 had always been very high, but 

 much worse in some years than 

 in others. The year 1896 was 

 unusually bad, and 1897 not 

 much better. Immediately after 

 the American army of occupation 

 began to clean up in Havana, 

 in 1898, the sanitary conditions 

 showed marked improvement. By 

 eliminating the breeding-places 

 of mosquitoes, yellow fever has 

 been completely banished from 

 the island 



reach them, the mosquitoes 

 essary to keep the borders 



246. Fighting mosquitoes. Each 

 one of us can keep on killing mos- 

 quitoes on sight and feel that he is 

 doing his duty, but the insects do 

 not recognize city limits or state 

 lines, and gayly fly from one man's 

 grounds to another's. So far the only 

 effective campaign against mosqui- 

 toes has been waged on a compre- 

 hensive scale by a whole community 

 at a time. It seems that the best 

 means of preventing malaria and 

 yellow fever are ( i ) ditches to drain 

 off marshy land; (2) cartloads of 

 dirt to fill in low-lying spots ; 

 (3) oil on such puddles as cannot 

 be filled or drained ; and (4) lids or 

 screens to cover up cisterns, tanks, 

 or buckets in which water must be 

 kept standing, while all old cans 

 and other possible containers for 

 water are scrupulously placed where 

 the female mosquito cannot reach 

 them, since the life history of the 

 mosquito calls for quiet water for 

 the laying of the eggs and for the 

 growth of the larva and the pupa. 

 Without such breeding-places one 

 year would see the end of all mos- 

 quitoes in all civilized communities. 

 In larger bodies of water, where fish 

 may be kept, these will usually de- 

 stroy the larvae ; but in the shallow 

 margins, where the fishes cannot 

 have things their own way. It is nec- 

 of ponds clear of weeds, sedges, etc. 



