9 



tion with the exhibit of the Bureau of Forestr} 7 . The exhibit shows 

 the character of work of some of the most destructive enemies of for- 

 ests and the insects which are responsible for the damage. The labels 

 give general information regarding the insects and their habits, which 

 will aid the forester and the lumberman in recognizing them when met 

 with. 



Section IV. —PHOTOGRAPHS OF INSECT DAMAGE TO FORESTS. 



The photographs of insect damage are enlarged from 4 by 5 and 5 

 by 7 negatives taken by the author and his assistants, and show some 

 of the features of insect work which could not well be represented by 

 specimens. 



GENERAL DESCRIPTION OF THE EXHIBIT. 



A large amount of the material in the exhibit represents the first of 

 the kind collected, and many of the descriptions of the work, host 

 plants, habits of the insects, etc. , on the labels and in this catalogue, 

 are original. 



The exhibit represents several quite distinct classes of enemies, as 

 related to orders and groups of insects, the parts of trees attacked, 

 primary or secondary injuries, etc. This is indicated to a certain 

 extent by the arrangement of the specimens in the cases, and by the 

 labels; but in order to prevent duplication in the catalogue, the 

 descriptions of the principal classes of insects and the character of 

 their work are included in the introduction, classified primarily accord- 

 ing to the part of the tree or kind of product injured, and secondarily 

 according to the class of insects which have similar habits. 



The term "trunk and branches" not only refers to living trees, but 

 to dying, dead, and felled trees, sawlogs, and like crude products. 



INSECTS INFESTING THE BARK. 



BARK-BEETLES. 



[Plates I-VIIL] 



This class of beetles attacks living, dead, and recently felled trees. 

 The parent adults excavate their brood galleries through the inner 

 layers of bark and often groove the outer surface of the wood. Their 

 eggs are deposited along the sides of the galleries and the young- 

 broods develop in the bark and transform to the adult either in the 

 bark or outer sapwood. Some of the species attack living trees, 

 causing their rapid death, and are among the most destructive enemies 

 of American forests; others are of secondary importance in attacking 

 the injured trees and contributing to their death, while still others 

 attack only the bark and twigs of dying and dead trees. 



