10 



BULLETIN" 1490, U. S. DEPARTMENT OF AGRICULTURE 



in the surrounding wood. In the latter case, the injury is caused by 

 the larvae or grubs (young) of the beetles. 



PINHOLE DEFECTS FORMED IN LIVING TREES; A NONPREVENTABLE LOSS 



When pinhole defects occur in the living tree, it is of course im- 

 possible for the lumberman to prevent the injury, since the holes < 



Fig. 9. — Pinholes with short stain streaks made in green ash lumber by Platypus 



compositus 



have been made periodically, and often many years before the tree 

 was cut. The dates when the injury was done can be determined 

 by counting the annual rings of tree growth. Usually the wood 

 surrounding pinholes of this type is stained. 



PINHOLES IN LIVING TREES CAUSED BY AMBROSIA BEETLES 



Pinholes are uniform in size, one-eighth of an inch in diameter or 

 smaller (to one twenty-fifth inch), either darkly stained or un- 



