4 MISC. PUBLICATION 74, U. S. DEPT. OF AGRICULTURE 



THE MOST IMPORTANT FOREST INSECTS 



This list includes those species of forest insects which are of the 

 greatest economic importance at the present time. In the discussion 

 of each species the common and technical names are given. There 

 is added some information on the occurrence of the insect, the char- 

 acter of damage or notable epidemics, and the most important or 

 available references to it in literature. 



For the convenience of those not acquainted with the systematic 

 classification of insects, the species listed have been arranged in 

 groups according to the type of damage, such as bark beetles, leaf 

 feeders, etc., and these groups are further subdivided as necessary. 



TREE-KILLING BARK BEETLES 



THE SOUTHERN PINE BEETLE 



Dendroctonus frontalis Zimm. 



In the southeastern part of the United States the southern pine 

 beetle stands out as the most important tree-killing bark beetle. This 

 species becomes exceedingly abundant at irregular intervals; and 

 for several years, during one of these outbreaks, thousands of pines 

 may be attacked and killed. In 1910 and 1911 timber valued at over 

 $2,000,000 was destroyed (1, Jfi, l$) x . 



THE EASTERN SPRUCE BEETLE 



Dendroctonus piceaperda Hopk. 



In past years, before the virgin spruce forests of the Northeast 

 were cut, this bark beetle was responsible for serious depredations. 

 Of late years little timber has been killed by this beetle in the United 

 States, though serious losses are reported from Canada (4%)» 



THE TURPENTINE BEETLES 



Dendroctonus valens Lee. 

 Dendroctonus terebrans Oliv. 



The red turpentine beetle {Dendroctonus valens) and the black 

 turpentine beetle (D. terebrans) are widely distributed in North 

 America. They attack the bases and roots of practically all species 

 of pine and spruce, causing the exudation of large masses of pitch. 

 They rarely kill trees and are of importance more as a result of the 

 attention they attract than because of the damage inflicted (i, 30, Jfi, 

 46). 



THE MOUNTAIN PINE BEETLE 



Dendroctonus monticolae Hopk. 



The mountain pine beetle has a very wide range, extending from 

 the Sierras of central California through the northern Rockies into 

 Canada. It attacks lodgepole, sugar, western white, and yellow pines. 

 Nearly every year severe outbreaks are in progress in some part of 

 this area. One notable infestation has been progressing since 1909 

 and now bids fair to destroy practically all the lodgepole pine on 

 the Bitter Root and Beaverhead National Forests (^1, #>). 



1 Reference is made by italic numbers in parentheses to Literature Cited, p. 23. 



