CIRCULAR No. 126. Issued Novcin.-i n;. I-.MO. 



United States Department of Agriculture, 



BUREAU OF ENTOMOLOGY. 



L. O. HOWARD, Entomologist and Chief of Bureau. 



INSECT INJURIES TO THE WOOD OF LIVING TREES.* 



By A. D. HOPKINS, 

 In CJtcirge of Forest Insect Investigations. 



It has been determined that insects of a certain class attack the 

 wood and bark of living timber and that, while they do not con- 

 tribute materially to the death of the trees or give much external 

 evidence of their presence, they produce wounds in the bark and 

 wormhole and pinhole defects in the wood which result in a depre- 

 ciation in commercial value amounting to from 5 to 50 per cent. 

 These defects in the wood are not detected until after the .trees have 

 been felled and the logs transported to the mill and converted into 

 lumber. Thus to the actual damage to the lumber is added the 

 expense of logging and manufacture of the defective, low-grade 

 material, much of which must be discarded as worthless culls. 



The oak timber worm. One of the most destructive of the class of 

 depredators just mentioned is the oak timber worm. It enters the 

 wood of the trunks of living trees through wounds in the bark and 

 at the base of broken or dead branches and extends its " pinhole " 

 burro\vs in all directions through the solid heartwood. The losses 

 occasioned by this insect in the hardwood forests of the eastern United 

 States are enormous and usually affect the wood of the finest ex- 

 amples of old trees. 



The chestnut timber worm. The chestnut throughout its range is 

 damaged in a like manner by the chestnut timber worm. Practically 

 every tree of merchantable size is more or less affected, and a large 

 percentage is so seriously damaged that the product is reduced to that 

 of the lowest grade. It is estimated that the reduction in value of the 

 average lumber product at any given time is not far from 30 per cent, 



Revised extracts from Bulletin No. 58, Part V, Bureau of Entomology, U. S. 

 Department of Agriculture. 1909. 

 63707 Cir. 12610 



