DEFECTS IN TIMBER CAUSED BY INSECTS 



11 



stained, or with short streaks in the surrounding wood; these holes 

 run deeply in every direction in an irregular manner through the 

 wood, and it is difficult to determine their extent from the surface. 

 The} 7 are termed "pinholes," "shot holes," or "black holes" (36). 

 Such holes occur in both the sapwood and heartwood of softwoods 

 and hardwoods, but are more common in the sapwood. 



One of the commonest defects (fig. 1) is caused in living trees by 

 an ambrosia beetle, 2 and the holes are known as " black holes," " spot 

 worm," "steamboats," 



fc*-'5' 



fi 



" grease spots " (West Vir- 

 ginia), and "flag worm'' 

 (Arkansas ) . The holes 

 usually occur in the best 

 part of the wood, either 

 one in a place, or two or 

 more in a row. This de- 

 fect is so prevalent in ma- 

 ture white oak and other 

 oaks that it is often diffi- 

 cult to find a tree the wood 

 of which is entirely free 

 from it ; in yellow poplar 

 the defect is not so com- 

 mon. When the defect 

 does occur in whitewood 

 or yellow poplar the ac- 

 companying long, black, 

 greenish or bluish streaks 

 give a calico effect, and the 

 wood is called " calico pop- 

 lar " (fig. 2) (23,27). The 

 same defect occurs in 

 beech, birch, basswood. 

 maple, and elm in West 

 Virginia, elm and oak in 

 Michigan, oak in Arkan- 

 sas, and chestnut in Ten- 

 nessee. 



Calico poplar and oak 

 might be used, when avail- 

 able in sufficient quantity, 

 as a special grade for in- 

 terior natural-wood finish, 

 as the effect is pleasing. 

 Thus the apparently limited quantity could be utilized without hav- 

 ing its value depreciated much below that of the first and second 

 grades. 



This defect causes a serious loss to stave and shingle stock. In 

 Arkansas from 30 to 40 per cent of white oak Bourbon whisky -barrel- 

 stave stock and staves has often been left to rot in the woods on 

 account of injury by the oak timber worms and ambrosia beetles. 



Fig. 10. 



-Pinholes made by Xyleborus sp. in green 

 chestnut board, after piling 



2 Corthylus columbianus Hopkins. 



