24 



BULLETIN 1490, U. S. DEPARTMENT OF AGRICULTURE 



wood of all kinds of timber. They may either be stained black 

 inside or be of the same color as the surrounding wood, and they 

 may be free and open or filled with tightly-lodged boring dust, 

 depending on the kind of insect making them. This boring dust 

 does not fall out when the wood is jarred. Grub holes are made in 

 the living tree, in the saw log, or in piled green lumber. In nearly 

 all cases the injury is caused by the young borers, sawyers, or grubs, 

 but occasionally also by adult termites or white ants (fig. 18), adult 



Fig. 26. 



-Wonnhole defects in cedar, caused by the round-headed borer Cullidium 

 antennatuin 



carpenter bees 13 (fig. 19), or carpenter ants 14 (fig. 20), or by the 

 larvae of horntails 15 (fig. 21). Usually this type of injury is con- 

 sidered as " wormholes, no living worms or decay," especially if the 

 holes are stained black, and no further damage will result, except 

 in rare cases. 



Grub holes constitute a standard defect and are also included 

 under " equivalent defects." They are often of considerable size 



13 Xylocopa spp. 



14 Gamponotus spp. 



15 Tremex oolumba L„ or Sirex spp. ; they usually damage only dead wood or trees or 

 logs that have been left in the woods too long. 



