DEFECTS IN TIMBER CAUSED BY INSECTS 



9 



The larvae of some types of ambrosia beetles excavate side gal- 

 leries at right angles to the gallery made by the adult, which tun- 

 nels into the wood to deposit eggs; other types excavate no side 

 galleries. Some holes are clear; others are stained black by the 

 action of fungi, some of which the beetles cultivate for food in their 



Fig. 7. — Pinholes caused by ambrosia beetles in heading 

 and tight cooperage in South Carolina 



Fig. 8. — Pinholes in green hickory lumber caused by an ambrosia beetle (Xyle- 

 borus xi/lographus) 



galleries. Injury to green heartwood stock and to partly seasoned 

 stock of such woods as hickory and cypress in many cases does not 

 produce the stain. 



These holes are always open (never filled with dust), and are 

 either clear or black and associated with discolored streaks or stains 



38252°— 27 2 



