INSECT DEPnKDATTOXS IN NORTH AMKHICAX I'ORES'I S. 73 



ditions and t'acilitii'^ fji\<»i"al)le and iiiif'av oi-ahlc U>v success in prac- 

 tical applications accordinir to the irconnncniletl method or policy (»f 

 control. 



As has been shown, the inatnre or merchantable timber is the most 

 susceptible to injury or death fi'om the rava<ies of insects. There- 

 fore, considered from the standpoint of insect c(uitrol and the pre- 

 vention of one of the ij^reatest 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 seasonal 

 history of each species which ditfer to a greater or less extent from 

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

 tain features in the characteristics of the various s^jecies 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 uuiny jieculiar features in the prevailing conditions 

 in diti'erent localities, some of them favorable, others unfavorable, for 

 the practical application according to a given method, so that while 

 certain general advice may apply in a l)road sense and be available 

 for utilization by the i)ractical man, whether owner, manager, or 

 forester, without further advice, it is often necessary to diagnose a 

 given case before specific expert advice can be given as to the exact 

 cause and the most etl'ective method or policy to be adopted, just as a 

 physician must diagnose a case of illness or injury before prescribing 

 the required treatment for his patient. 



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

 ■waste of forest resources caused by insects can be j^revented and how 

 far the damaged timber can l)e utilized, we will attempt to give oidy 

 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 injuries 

 to the wood of living timbei". C^) ivduce 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 coiulitions and 

 opportunities for success in the general control of forest insects. 



coNTRoi. OK harkiikkti.ks Willi n mm. iitr.Ks. 



The barkbcctles which l<ill tree- ati!icl< the bark- on ilie trunk and 

 destroy the life of the tree l»y extending their i)urrows or galleries in 

 all directions through the imier living bark. The l)roo(ls of younL*" 

 grubs or larva' develop within the inner bark, on which they feed. 



