92 SOME INSECTS INJURIOUS TO FOEESTS. 



Billions of feet of matured spruce have been killed by the eastern 

 spruce beetle during the past half century in the northeastern United 

 States and southeastern Canada (p. 58). 



A large percentage of the matured Engelmann spruce of the Eocky 

 Mountains region has been killed by the Engelmann spruce beetle 

 within the past fifty years (p. 59). 



A large percentage of the pine timber of merchantable size in the 

 Black Hills National Forest and other national and private forests of 

 the central Eocky Mountains region has been killed during the past 

 ten years by the Black Hills beetle (p. 59). 



A large percentage of the best matured pine timber of the region 

 north and west of Colorado and Utah has been killed within the past 

 twenty years by the mountain pine beetle and the western pine beetle 

 (p. 59). 



A large percentage of the matured Douglas fir, or red fir, of the 

 Eocky Mountains region has been killed by the Douglas fir beetle 

 (p. 59). 



The supply of hickory timber in the forests and woodlots of the 

 States east of the Mississippi Eiver has been greatly reduced by the 

 ravages of the hickory barkbeetle (p. 60). 



Practically all of the matured eastern larch has been killed over 

 vast areas in the northeastern United States and southeastern Canada 

 by the larch worm and eastern larch beetle (p. 60). 



The wood of living timber has been rendered defective by wood- 

 boring insects to such an extent as to reduce the value of a vast 

 amount of standing timber from 50 to 75 per cent (p. 60). 



Eapid deterioration of the wood of dying and dead trees has been 

 caused by wood-boring insects, often amounting to from 25 to 100 

 per cent during the period in which it would otherwise be available 

 for utilization (p. 62). 



Crude manufactured and finished forest products have been dam- 

 aged by insects to such an extent as to cause an estimated average 

 annual loss of 10 per cent of its mill value (pp. 64-67). 



Insects are the cause of greatly reducing our forest resources by 

 killing the inaccessible timber; by reducing the quantity through 

 injuries to the wood of living and dying timber ; by preventing nor- 

 mal reproduction and development of future supplies, and through 

 destroying forest products. 



GENERAL ESTIMATES OF AMOUNT OF DAMAGE CAUSED BY FOREST INSECTS. 



The results of extensive observations during the past ten years in 

 the principal forested areas of all sections of the country, and during 

 an additional eight years in West Virginia, indicate to the writer 

 that the amount of standing timber killed by insects, together with 



