194 SCIENCE REMAKING THE WORLD 



In other cases the cultural practices are changed in 

 efforts to affect the life of injurious insects. Or, as in 

 the case of the California white scale and the Australian 

 ladybird, the entomologist attempts to use the natural 

 enemies of insects in his warfare. 



The importation of the Australian ladybird into 

 California in the late 'eighties to kill off the white scale 

 which threatened the extinction of the orange and lemon 

 growing industries was a great accomplishment in itself 

 and saved the country many millions of dollars. It is 

 of especial significance, however, in that it pointed out 

 the possibility of the utilization of the natural enemies 

 of destructive insects, particularly those accidentally 

 imported from one country into another, in such a way 

 that it has been followed with other successes in this 

 country and elsewhere. 



We need only refer to the gipsy moth and the brown* 

 tail moth to realize the importance of these kinds of 

 investigation cited above. It has been possible to re- 

 tard the spread of the gipsy moth for many years and 

 practically to confine it to New England largely by the 

 development of spraying methods which render possible 

 the spraying of large forested areas. During a number 

 of years parasites of different kinds were imported from 

 all parts of Europe and from Japan. Several species 

 of these parasites have become established in this coun- 

 try, and it is due largely to their work that the brown- 

 tail moth has become greatly reduced in number and 

 that the area over which it had spread has become 

 greatly restricted. And it is also due to these parasites, 

 at least in part, that in the Boston metropolitan dis- 



