INSECT DAMAGE IN THE NATIONAL PARKS. 9 



turn are checked or repelled by natural means, so that generations 

 of younger trees take the place of their ancestors, and the forest as 

 such is perpetuated. 



Natural control the most expensive. — In the national parks, na- 

 tional forests, and private forests where the resources have a commer- 

 cial value this natural control of the insect depredators on the 

 timber is the most expensive and wasteful. Our friends, the enemies 

 of the beetles, can not be depended upon to operate for the best 

 interests of the Federal or private owner. They can, however, be 

 made to render efficient service as the allies of the owner in an aggres- 

 sive warfare by him against the invaders. In this capacity they are 

 indispensable in the defense against renewed attacks and in the main- 

 tenance of conditions which will insure the future protection of the 

 living timber. 



GENERAL METHODS OF CONTROL. 



It is through a knoAvledge of the habits and seasonal history of the 

 various species of depredating insects, and the various complex fac- 

 tors operating for and against them, that forest entomologists are 

 enabled to advise methods of procedure in practical control opera- 

 tions either to reduce or eliminate the favorable conditions for the 

 multiplication of the beetles or to promote and utilize the factors 

 that are unfavorable for their existence. 



It is also through a knowledge of the characteristic evidences of 

 their presence in the living and dying trees that we are enabled to 

 give instructions to an experienced timber cruiser, forest ranger, or 

 fire patrolman which will enable him readily to detect an infestation 

 and report upon its character and extent. 



Experiments with and demonstrations of methods of control have 

 furnished up-to-date information on the essential requirements in 

 conducting active control operations, which enables us to advise the 

 most economical and effectual method to be adopted for each species 

 of beetle, each species of tree, and each locality where an infestation 

 prevails. 



Therefore, if the symptoms are accuratelj^ described and informa- 

 tion is furnished as to the local facilities for utilizing the infested 

 timber or for treatment at direct expense, specific recommendations 

 for successful control can be made without an examination by an 

 expert. 



The presence in any national park of quantities of dying pine, 

 spruce, or Douglas fir that has not been caused by recent fires is 

 evidence of the presence and destructive work of one or more species 

 of the Dendroctonus beetles. An examination of the bark of the 

 main trunks of some of the dying trees will usually furnish conclusive 

 evidence, for if the trees are infested the characteristic work in the 



