88 



THE DESTRUCTI\"E AGENTS OF FORESTS. 



investigations for the United States Department of Agriculture 

 furnish valuable information in regard to practically all our 

 species of forest insects that are of serious consequence. The 

 writer in preparing this chapter has dra^^-n freely from these 

 publications as representing the best knowledge to be had on the 

 subject. 



Nature and Extent of Injury. 



The damage done by forest insects, in the opinion of those 

 who have investigated the subject most, is in excess of that done 

 by forest fires. The destructive work of the two agents, however, 

 is often reciprocal, the one agent assisting and furthering the de- 

 struction begun by the other. Thus it happens often that where 

 insects have injured and killed forest trees fires will follow and 

 burn the inflammable dead wood with great devastation. Like- 

 wise, timber injured or killed by fires invites many species of 

 bark and wood boring insects which further the work of destruc- 

 tion. In both cases the injury from the lairning is the more con- 

 spicuous and the fires are usually accredited with the major por- 

 tion of the loss, when, in fact, the insects may be the more de- 

 structive agent of the two. The interrelations of forest insects 

 and wood-destroying fungi are also frcriuently very marked. The 

 burrows of insects in the wood afi'ord suitable places for the fungi 

 to begin their work of decay, and. transversely, trees injured 

 primarily by fungi are attacked by insects and the progress of 

 deterioration and decay hastened. 



Insects injure forests by attacking tlie bark, wood and 

 foliage of living trees causing their death or a more or less seri- 

 ous impairment of their health and of the quality of the lumber 

 which they may produce. Standing diseased or dead trees and 

 felled trees and logs are attacked by other species that bore 

 through the wood and cause great loss. ]\Ianufactnred lumber, 

 both in the rough and finished, and tanbark are often injured. 

 The seeds of various forest trees are attacked by other species 

 and injured so that they will not germinate when planted thus 

 interfering with both natural and artificial ret'orestatiou. 



The following is a brief description of some of the more de- 



