PROTECTION FROM OTHER AGENCIES 317 



was used in the attempt to control the invasion of the 

 bark-beetle in the Black Hills. Special tools were de- 

 veloped for removing the bark of standing trees. Where 

 the trees cannot be utilized, the design is to cut or peel 

 only such trees as are absolutely necessary to check the 

 spread of the insects. Ordinarily it is necessary under such 

 conditions to employ an expert, who is thoroughly 

 familiar with the habits of the beetle, to select the trees, 

 in order to secure the greatest possible economy in the 

 work. 



In the case of some insects, control work is conducted 

 by the use of so-called trap-trees. Thus, in the case of 

 insects which breed in fallen logs, tops, stumps, etc., 

 trees may be felled here and there as traps. The insects 

 are attracted to them as breeding-places. At the right 

 season of the year the bark is removed and the broods 

 destroyed. 



Other measures are used in the case of certain defo- 

 liating insects. At the present time drastic measures are 

 being used to suppress the outbreak of gipsy and brown- 

 tail moths in the Northeast. Various measures are used, 

 including the destruction of egg masses where these can 

 be reached, the wrapping of trees with burlap or tangle- 

 foot, and wholesale spraying with high-power spraying 

 machines. This work is expensive, but it is necessary 

 to protect property which will inevitably be destroyed 

 unless the insects are checked. 



The above illustrations show the general character of 

 the work required in controlling an insect invasion. They 



