* THE SCOLYTTD BEETLES. 



wick during the past centuiy (Hopkins, 1901a), the widespread 

 destruction of pine and spruce by the southern pine beetle (No. 4) 

 in West Virginia and Virginia in 1891 and 1892 (Hopkins, 1899a), the 

 destruction of a large percentage of the timber in an entire National 

 Forest by the Black Hills beetle (No. 10) within the past ten years 

 (Hopkins, 1902& and 1905), and the depredations by the western 

 pine beetle (No. 1) in Idaho, Oregon, and California (Webb, 1906), 

 and by the mountain pine beetle (No. 9) in Wyoming, Montana, 

 Idaho, Oregon, Utah, and California noted in the present paper. 



CHARACTER AND EXTENT OF DEPREDATIONS. 



Living healthy trees are attacked by swarms of the adult beetles, 

 which enter the bark on the main trunk and excavate their egg 

 galleries for a distance of a foot or more through the inner, living 

 bark. This weakens the vitality of the tree, and in addition the 

 larvse hatching from the eggs mine through and destroy the bark 

 intervening between the egg galleries, thus completely girdling the 

 trees and causing their death. The amount of timber killed in 

 this manner during the past century has been enormous. That 

 known to have been killed by these beetles in West Virginia, New 

 England, and the Black Hills National Forest alone amounts to many 

 billions of feet of the best pine and spruce, to say nothing of the 

 less conspicuous depredations each year scattered through the 

 forested sections of the Rocky Mountain, Cascade, Sierra, and Coast 

 regions, and of the Southern States. Very conclusive evidence has 

 also been found that some of the great denuded areas in the Rocky 

 Mountains region supposed to have been caused by forest fires were 

 primarily caused by one or more species of Dendroctonus. From 

 our present knowledge of the facts and evidence it is probable 

 that if the timber destroyed by these insects in the United States 

 during the past fifty years were living to-day its stumpage value 

 would be more than 11,000,000,000. 



POSSIBILITIES OF CONTBOL. 



The results of our investigations, experiments, and practical 

 demonstrations make it clear that wherever private forests or State 

 or National forests are under organized management for fire pro- 

 tection and economic utilization the control of these insects is often 

 a less difficult and less expensive problem than that of controlling 

 forest fires. In fact, wherever there is a sufficient demand for the 

 timber, and where facilities for the utiUzation of the trunks of the 

 infested trees within a specified time exist, tlie desired control may 

 often be brought about and maintained practically without cost 

 or even at a profit, especially if the action be taken before the depre- 

 dators have spread over extensive areas. 



