ENTOMOLOGY 319 



insects and establish unfavorable conditions for their future multipli- 

 cation or continuance of destructive work. 



It is, however, of the utmost importance that any adjustment or 

 modification in management or business methods should be based on 

 expert technical knowledge or advice relating to the species, habits, 

 life history, and natural enemies of the insects involved and the es- 

 sential features of the methods for their control. This should be 

 supplemented by expert knowledge or advice on the principles of 

 technical and applied forestry in the proper management, care, and 

 utilization of the forest and its resources, and still further supple- 

 mented by practical knowledge and experience relating to local con- 

 ditions and facilities favorable and unfavorable for success in prac- 

 tical applications according to the recommended method or policy of 

 control. 



As has been shown, the mature or merchantable timber is the 

 most susceptible to injury or death from the ravages of insects. 

 Therefore, considered from the standpoint of insect control and the 

 prevention of one of the greatest items of loss, it is important that 

 such matured timber should be utilized before it begins to deteriorate, 

 or before it reaches the stage of unprofitable growth. 



For the greatest success in dealing with forest insects, it must 

 be recognized that there are certain features in the habits and sea- 

 sonal history of each species which differ to a greater or less extent 

 from those of all other species, even of the same genus ; that there are 

 certain features in the characteristics of the various species of trees 

 which differ from those of all other species; and that as a rule it is 

 the technical knowledge of these peculiar features or characteristics 

 of the trees and their enemies which furnishes the clew to successful 

 methods of control. 



There are also many peculiar features in the prevailing condi- 

 tions in different localities, some of them favorable, others unfavor- 

 able, for the practical application according to a given method, so 

 that while certain general advice may apply in a broad sense and be 

 available for utilization by the practical man, whether owner, mana- 

 ger, or forester, without further advice it is often necessary to diag- 

 nose a given case before specific expert advice can be given as to the 

 exact cause and the most effective method or policy to be adopted, just 

 as a physician must diagnose a case of illness or injury before pre- 

 scribing the required treatment for his patient. 



Therefore, in a consideration of the problem as to how far the 

 waste of forest resources caused by insects can be prevented and how 

 far the damaged timber can be utilized, we will attempt to give only 

 general statements based on the results of our observations relating 

 to some of the principal kinds of loss discussed in the first part of 

 this paper, namely, by insects which (1) kill the trees, (2) cause in- 

 juries to the wood of living timber, (3) reduce future supplies, and 

 (4) cause injuries to the manufactured products. In addition, we 

 will consider the utilization of natural enemies of injurious insects, 

 the utilization of damaged timber, and the present conditions and 

 opportunities for success in the general control of forest insects. 



