DEFECTS IN TIMBER CAUSED BY INSECTS 



23 



Under present methods of lumbering, such imported logs usually 

 are infested by pinhole-boring beetles of many species, which attack 

 the logs after they are cut, and continue to live in them for several 

 months and in some cases a year or more. If such logs are shipped 

 into another country with a similar climate, the insects may survive 

 and attack logs of native timber; if, on the other hand, logs are 

 exported to a much colder or hotter country, the insects will rarely, 

 if ever, become established in the country of import. 



There is, therefore, some danger of introducing destructive species 

 through the commercial interchange of timber in the form of logs. 



Fig. 25. — Wormholes caused by " sawyers " (Monochamus spp.) in pine. A and B, 

 wormholes in southern yellow pine ; C, wormholes in white pine 



For example, many insect species are widely distributed over tropical 

 America that do not occur in tropical Africa, Asia, Australasia, 

 and the Pacific islands. Tropical Australia, the Philippine Islands, 

 and tropical Japan doubtless have a considerable number of the 

 same species of pinhole borers. One country may have a few that 

 do not occur in the others. 



DEFECTS CLASSED AS GRUB HOLES OR WORMHOLES 



Grub holes are medium to large, circular, oval, or irregular holes 

 from three-eighths to 1 inch in diameter, in both sapwood and heart- 



