160 



MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



in the wood from which fine powder exudes are a good indication of 

 their presence. 



Favorable conditions for attack are made when the sapwood of 

 fine-quality hardwoods, especially of hickory, ash, and oak, is 

 allowed to season for 2 or 3 years in undisturbed piles. Accumula- 

 tions of old stock, refuse, and useless material greatly increase the 

 hazard of infestation. Species of hardwood ordinarily not subject 

 to the attack of these insects will, if piled with more favorable host 

 species, share the damage of infestation. It is, therefore, evident 



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Figure 80. — Wood showing holes made by Lyctus beetles. 



that proper methods of handling will do much to prevent these de- 

 structive pests from becoming established. Material should be 

 inspected and rehandled annually, and all sapwood refuse, as well 

 as stock showing signs of infestation, should be burned. Woods of 

 different species should be piled separately and should be classified 

 according to age of seasoning, in order that a constant turn-over in 

 yard stocks may be maintained by utilizing or disposing of the long- 

 est-seasoned stock first. The use of heartwood instead of sapwood 

 for piling sticks in the yard also helps to reduce the breeding ground. 

 Kiln drying and steaming under pressure have produced gratifying 

 control. An undesirable feature of the steam-pressure methods is 

 that it is liable to lower the structural strength of the wood, and also 

 there is danger of causing discoloration. 



Stout's bostrichid {Polycaon stouti Lee.) is a large black beetle 

 about three-fourths of an inch long, with prominent mandibles. The 

 larvae bore in the wood of various hardwoods such as oak, eucalyp- 

 tus, maple, California laurel, madroha, sycamore, and other trees in 

 California. In several cases these larofe beetles have emerofed from 



