196 SCIENCE REMAKING THE WORLD 



cheaper as time goes on, and there is a good chance that 

 the airplane may be used in community dusting to great 

 advantage. 



The ravages of the pine bark-beetles in the far north- 

 western forests in past years have caused enormous 

 loss. Some people have said that this loss has been as 

 great as that from forest fires. These beetles have been 

 carefully studied from all points of view by Dr. A. D. 

 Hopkins and his associates, and it has resulted that 

 when an epidemic of these beetles has gained a start it 

 is now possible, by felling only a certain percentage of 

 the infested trees, to arrest the plague, while the ex- 

 pense of the operation is largely borne by the value of 

 the felled trees. This, however, has to be done at a 

 certain time of the year, namely in the month of April, 

 and the trees must be marked by trained scouts who 

 explore the forests during the previous autumn and 

 winter. A clean-up of this kind has just been made in 

 southern Oregon and northern California by coopera- 

 tive work of the Interior Department, the Forest Ser- 

 vice, the Bureau of Entomology, and private owners, 

 the operations being directed by a trained entomolo- 

 gist. 



At the present time more than 140 distinct projects 

 are being investigated by the federal bureau, and these 

 projects involve possibly five hundred of the species of 

 insects most injurious to crops, domestic animals, 

 stored foods, forest products, shade trees, and ornamen- 

 tal plants. It is safe to say that some form of remedial 

 treatment has been found for almost every markedly 

 injurious insect in the United States; but continued 



