310 THE PRINCIPLES OF HANDLING WOODLANDS 



The subject of forest entomology is, therefore, of 

 great importance in the practical handling of woodlands. 

 It is just as essential to protect the forests from in- 

 sect invasions as from rire. The protective measures 

 which must be used depend entirely upon the nature 

 of the attack, and hence upon the species of insect doing 

 the work. It is necessary to understand the life history 

 of the different insects and the manner in which they 

 work under different conditions, in order to be able to 

 prescribe measures for their control. The list of in- 

 jurious insects is very large, and it would be entirely 

 beyond the scope of this book to include an adequate de- 

 scription even of the more important genera. This in- 

 formation must be obtained from special works on forest 

 insects. The purpose here is to call attention to the im- 

 portance of the subject and to explain some of the general 

 principles of the problem. Information regarding insects 

 attacking the forests of the United States may be obtained 

 from the publications of the Bureau of Entomology of 

 the U. S. Department of Agriculture, especially the 

 works of Dr. A. D. Hopkins, who has taken the lead in 

 developing Forest Entomology in this country. 



Death of Trees. — The most extensive damage is done 

 by bark-beetles, which burrow in the inner bark of the 

 trunk and girdle the trees. Coniferous forests in partic- 

 ular suffer from the attacks of various bark-beetles. It 

 is very common in the coniferous forests to see here and 

 there trees or groups of trees turning red and dying. A 

 close examination usually reveals small perforations in 



