ENTOMOLOGY 311 



has contributed greatly to the destruction of the larch throughout 

 the northeastern United States and southeastern Canada. 



The Hickory Barkbeetle. Within the past ten years the hick- 

 ory barkbeetle has caused the destruction of an enormous amount of 

 hickory timber throughout the northern tier of States from Wiscon- 

 sin to Vermont and southward through the eastern Atlantic States 

 and into the Southern States as far as central Georgia. 



The Larch Worm. There are also many examples of wide- 

 spread depredations chargeable to insects which defoliate the trees, 

 thus contributing to their death. Notable among these are the dep- 

 redations by the larch worm, which, during several extensive out- 

 breaks since 1880, has killed from 50 to 100 per cent of the mature 

 larch over vast areas in the northeastern United States and south- 

 eastern Canada. It is evident that the amount of merchantable- 

 sized timber that has died as the result of defoliation by this insect 

 will aggregate many millions of feet. 



INSECT INJURIES TO THE WOOD OP LIVING TREES. 



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

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

 ute materially to the death of the trees or give much external evi- 

 dence of their presence, they produce wounds in the bark and worm- 

 hole and pinhole defects in the wood which result in a depreciation 

 in commercial value amounting to from 5 to 50 per cent. These de- 

 fects in the wood are not detected until after the trees have been 

 felled and the logs transported to the mill and converted into lum- 

 ber. 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 pin- 

 hole burrows 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 

 examples 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 reduc- 

 tion in value of the average lumber product at any given time is not 

 far from 30 per cent, thus involving extensive waste and an in- 

 creased drain on the forest to supply the requirements for clear lum- 

 ber. This insect also attacks the oaks, and especially the red oak, 

 the older trees of which are often as seriously damaged as are the 

 chestnut. 



Carpenter Worms. The oaks, especially the white oak and the 

 red oak, are seriously damaged by carpenter worms. The holes 

 made by these insects through the heartwood of the best part of tho 



