PINHOLES 



Pinholes are small, round, usually open holes ranging from one 

 one-hundredth to one-fourth of an inch in diameter; they are made 

 either by ambrosia beetles or timber worms. Pinholes caused by 

 ambrosia beetles are of two types: (1) Pinholes caused by adult 

 beetles boring into the trunks of growing trees for the purpose of 

 laying eggs and rearing their young, or by larvae, which also may 

 burrow in the wood; (2) pinholes made by adult beetles or larvae in 

 freshly felled green saw logs (with or without the bark on), bolts, 

 and green or partly seasoned lumber. 



In commercial grading rules for various species of timber pin- 

 holes constitute a standard defect (considering only wormholes), but 

 are sometimes recognized as " equivalent defects," that is, equivalent 



Fig. 3. — Work of ambrosia beetles in both sapwood and heartwood of southern 



yellow pine 



to other defects, such as knots. This grade in certain hardwoods is 

 termed " sound wormy " and is of that class of defects in timber or 

 lumber in which the insects are no longer present and hence no fur- 

 ther damage results to the timber. 



GRUB HOLES 



Grub holes or the larger wormholes are oval, circular, or irregular 

 holes three-eighths of an inch to 1 inch in diameter, produced by 

 adult insects (1) boring into or laying eggs in the trunks of living 

 trees, or (2) boring into green, recently felled logs for the purpose 

 of laying eggs or rearing their young; the young or larvae cause 

 most of the injury to the wood, which serves as both food and 

 shelter. 



Grub holes may also be classified as standard defects. 



